U.S. patent application number 15/407163 was filed with the patent office on 2017-05-04 for system and method for calibration of an optical module.
The applicant listed for this patent is INPHI CORPORATION. Invention is credited to Todd ROPE.
Application Number | 20170126313 15/407163 |
Document ID | / |
Family ID | 57795034 |
Filed Date | 2017-05-04 |
United States Patent
Application |
20170126313 |
Kind Code |
A1 |
ROPE; Todd |
May 4, 2017 |
SYSTEM AND METHOD FOR CALIBRATION OF AN OPTICAL MODULE
Abstract
A system and method for calibrating an optical module. The
optical module including a microprocessor with non-volatile memory
is provided at a calibration station for measuring calibrated value
of a device parameter against raw values starting from minimum
value in each of multiple zones of a primary parameter with one or
more secondary parameters at least being set to a basis calibration
point to determine coefficients for generating a N-spline function
for the multiple zones and multiple multipliers for each zone
corresponding to multiple calibration points. The coefficients and
multiple multipliers are stored in the non-volatile memory and
reused respectively for calculating a basis calibrated value based
on any current raw value of the primary parameter a N-spline
function in particular zone and for determining a final multiplier
by interpolation of the multiple multipliers associated with the
one or more secondary parameters, leading to a calibrated value for
any condition.
Inventors: |
ROPE; Todd; (Glendale,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INPHI CORPORATION |
Santa Clara |
CA |
US |
|
|
Family ID: |
57795034 |
Appl. No.: |
15/407163 |
Filed: |
January 16, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14860548 |
Sep 21, 2015 |
9553663 |
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15407163 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 10/0775 20130101;
H04B 10/07957 20130101; H04B 10/07955 20130101; H04B 10/40
20130101 |
International
Class: |
H04B 10/077 20060101
H04B010/077; H04B 10/079 20060101 H04B010/079 |
Claims
1. A method of using a calibration system for performing
calibration of a device parameter of an optical module, the method
comprising: setting up a calibration system, the calibration system
comprising: an optical module comprising an internal logic control
unit with non-volatile memory and an Analog and Digital
communication unit configured to control all internal optical
devices to obtain raw values of a selected primary parameter sorted
in N (N.gtoreq.1) zones at all operation conditions including
adjustments of one or more secondary parameters, a software
embedded in the internal logic control unit for executing a
calibration operation of the selected device parameter to deduce a
calibrated value in any current operation condition using both a
N-spline function of the selected primary parameter in each of the
N zones and an adjustment multiplier associated with the one or
more secondary parameters for each zone stored in the non-volatile
memory, and a data communication interface configured to report the
calibrated value; a calibration station comprising equipment to
adjust the one or more secondary parameter, a test data
communication bus connecting the host to one or more pre-calibrated
measurement equipments configured to provide calibrated
measurements of the selected device parameter, a test data
generation block for data communication between the optical module
and the host, a computer loaded with calibration software for
assisting measurements of the selected primary parameter and the
one or more secondary parameters, performing logic operation in
defining the N zones, sorting measurement data in each zone,
calculating coefficients for generating the N-spline function for
the N zones, deducing multiple multiplicative factors for multiple
value vertices of the one or more secondary parameters for each
zone, storing at least the coefficients for generating the N-spline
function and the multiple multiplicative factors into the
non-volatile memory of the optical module via a digital
communication interface; wherein the calibrated value for the
selected device parameter at any current operation condition is
obtained by operating the internal logic control unit to calculate
a basis-point calibrated value using the N-spline function
generated by the coefficients for at a particular zone of the
selected primary parameter corresponding to the current operation
condition, to calculate the adjustment multiplier by interpolating
the multiple multiplicative factors with corresponding weights
depended on the one or more secondary parameters at the current
operation condition with respect to at least two calibration
points, and to multiply the adjustment multiplier to the
basis-point calibrated value; determining an order n of a
polynomial function for each of the N zones wherein n.gtoreq.0 and
is varied for the N zones; performing calibration measurements for
each of the N zones.
2. The method of claim 1 wherein performing calibration
measurements for each of the N zones comprises performing a first
plurality of calibration measurements in the selected zone, with
the one or more secondary parameters being set at corresponding
values selected as a basis point, to obtain a plurality calibrated
values of the device parameter measured by a pre-calibrated
measurement equipment respectively against a plurality of raw
values of the selected primary parameter in the selected zone
measured by the optical module to deduce n+1 number of
coefficients.
3. The method of claim 2 wherein performing calibration
measurements for each of the N zones further comprises: performing
a second plurality of calibration measurements respectively at a
second plurality of calibration points to generate a multiplicative
factor of the selected zone for each calibration point; and storing
the n+1 number of coefficients for constructing the order n
polynomial function and the multiplicative factor associated with
each of the second plurality of calibration points for the selected
zone into the non-volatile memory.
4. The method of claim 1 further comprising generating the N-spline
function for all N zones based on each order n polynomial function
for each zone at the basis point, the N-spline function being
programmed into the internal logic control unit for generating a
basis-point calibrated value of the device parameter for the
optical module.
5. The method of claim 1 wherein the selected primary parameter is
one of the plurality of primary parameters comprising optical power
including internally generated power from a laser source and
externally transmitted or received power, optical modulation
amplitude for both transmitted and received signal, laser
frequency/wavelength per channel and wavelength shift from a target
value, module temperature, power supply voltage, optical bias
current, and thermo-electric cooler current, among which the device
parameter is selected for calibration against at least the selected
primary parameter.
6. The method of claim 1 wherein the each of the one or more
secondary parameters comprises at least module temperature and
power supply voltage and is interchangeable with one of the
plurality of primary parameters.
7. The method of claim 1 further comprising concurrently selecting
at least a second primary parameter determined with alternate
multiple zones together with the selected primary parameter with
the N zones for generating a multi-zone function for calculating a
basis-point calibrated value of a single device parameter at all
operation conditions against at least two primary parameters.
8. The method of claim 1 wherein the first plurality of calibration
measurements for each zone comprises measurements of the
corresponding calibrated values of the device parameter with the
selected primary parameter at least being a starting minimum value
in the selected zone and being a starting minimum value in a next
higher zone with options of being one or more intermediate values
in the selected zone to use a least squires fit method for
determining the n+1 coefficients.
9. The method of claim 1 wherein the second plurality of
calibration measurements for each zone comprises measurements of
the corresponding calibrated values of the device parameter
measured by the pre-calibrated measurement equipment with the one
or more secondary parameters at least being set once at the basis
point at which the corresponding multiplicative factor is set to 1
and with the selected primary parameter at least being a starting
minimum value in the selected zone.
10. The method of claim 1 wherein each calibration point
corresponds to a set of values of the one or more secondary
parameters, wherein among the second plurality of calibration
points each of the one or more secondary parameters is adjusted by
the calibration station with at least two different values
including the correspond value at the basis point.
11. The method of claim 10 wherein the two different values are
preferred to cover substantially wide operation range of the
corresponding one secondary parameter in the optical module.
12. The method of claim 1 wherein deducing each of multiple
multiplicative factors comprising taking ratio, after a necessary
unit conversion, of a corresponding calibrated value measured by
the pre-calibrated measurement equipment at the corresponding
calibration point with respect to the calibrated value at the basis
point.
13. The method of claim 1 wherein generating the N-spline function
comprises connecting each order n polynomial function for each of
the N zones by defining a boundary condition with all 1st through
(N-1)th derivatives being equal at a boundary point between the
selected zone and a next higher zone, the boundary point
corresponding to a maximum raw value of the selected zone being
equal with a minimum raw value of the next higher zone.
14. The method of claim 1 wherein the calibration station comprises
at least a software loaded with the aid of a computer through a
data communication interface, for each of the first plurality of
calibration measurements for each zone, to assist adjustment and
measurement of each raw value of the selected primary parameter,
measurement of each calibrated value of the device parameter, and
calculation of the n+1 coefficients for the order n polynomial
function, and for each of the second plurality of calibration
measurements for each zone, and to assist adjustment of each of the
second plurality of calibration points, measurement of each set of
values of the one or more secondary parameters, and conversion of
each measured calibrated value to a numerical unit, and calculation
of each multiplicative factor.
15. The method of claim 14 wherein the software comprises a
plurality of computer executable instructions to save all types of
data for each zone obtained during the first and second plurality
of calibration measurements via the data communication interface to
the non-volatile memory in the internal logic control unit, the all
types of data for each zone including all raw values from the
starting minimum value of the selected primary parameter, the
calculated n+1 coefficients for constructing the polynomial
function of order n, all multiplicative factors, and all sets of
values of the one or more secondary parameters respectively at the
second plurality of calibration points.
16. The method of claim 14 wherein the non-volatile memory
comprises a data structure configured to sort each type of the all
type from a lower value to a higher value.
17. A method of delivering a calibrated device parameter of an
optical module from a calibration system to a host, the method
comprising: coupling an calibration system to a host, the
calibration system comprising: an optical module comprising an
internal logic control unit with non-volatile memory and an Analog
and Digital communication unit configured to control all internal
optical devices to obtain raw values of a selected primary
parameter sorted in N (N.gtoreq.1) zones at all operation
conditions including adjustments of one or more secondary
parameters, a software embedded in the internal logic control unit
for executing a calibration operation of the selected device
parameter to deduce a calibrated value in any current operation
condition using both a N-spline function of the selected primary
parameter in each of the N zones and an adjustment multiplier
associated with the one or more secondary parameters for each zone
stored in the non-volatile memory, and a data communication
interface configured to report the calibrated value; a calibration
station comprising equipment to adjust the one or more secondary
parameter, a test data communication bus connecting the host to one
or more pre-calibrated measurement equipments configured to provide
calibrated measurements of the selected device parameter, a test
data generation block for data communication between the optical
module and the host, a computer loaded with calibration software
for assisting measurements of the selected primary parameter and
the one or more secondary parameters, performing logic operation in
defining the N zones, sorting measurement data in each zone,
calculating coefficients for generating the N-spline function for
the N zones, deducing multiple multiplicative factors for multiple
value vertices of the one or more secondary parameters for each of
the N zones, storing at least the coefficients for generating the
N-spline function and the multiple multiplicative factors into the
non-volatile memory of the optical module via a digital
communication interface; wherein the calibrated value for the
selected device parameter at any current operation condition is
obtained by operating the internal logic control unit to calculate
a basis-point calibrated value using the N-spline function
generated by the coefficients for at a particular zone of the
selected primary parameter corresponding to the current operation
condition, to calculate the adjustment multiplier by interpolating
the multiple multiplicative factors with corresponding weights
depended on the one or more secondary parameters at the current
operation condition with respect to at least two calibration
points, and to multiply the adjustment multiplier to the
basis-point calibrated value; measuring a current raw value of the
selected primary parameter at a current set of values of the one or
more secondary parameters; determining the current raw value in a
first zone of the N zones if the current raw value is greater than
a first starting value of the first zone and smaller than a first
starting value of a second zone; generating a basis-point
calibrated value of said selected device parameter based on the
current raw value using the N-spline function in the first zone;
performing a multi-linear interpolation based on the current set of
values and multiple sets of the plurality of sets of values of the
one or more secondary parameters for the first zone to calculate a
first adjustment multiplier; performing a multi-linear
interpolation based on the current set of values and alternative
multiple sets of the plurality of sets of values of the one or more
secondary parameters for the second zone to calculate a second
adjustment multiplier; interpolating between the first adjustment
multiplier and the second adjustment multiplier to obtain a final
multiplier; and multiplying the final multiplier to the basis-point
calibrated value to obtain a final calibrated value of the selected
device parameter communicated to the host.
18. The method of claim 17 wherein said selected device parameter
of the optical module is one selected from optical power including
internally generated power from a laser source and externally
transmitted or received power, optical modulation amplitude for
both transmitted and received signal, laser frequency/wavelength
per channel and wavelength shift from a target value, module
temperature, power supply voltage, optical bias current, and
thermo-electric cooler current, among which at least one is the
selected primary parameter being utilized as a variable of the
N-spline function.
19. The method of claim 17 wherein one or more secondary parameters
comprises at least module temperature and power supply voltage.
20. The method of claim 17 further comprising performing automatic
unit conversion between any calibrated value of the device
parameter and corresponding raw values of the primary parameter and
the one or more secondary parameters.in the internal control logic
associated with all calibration measurements before performing any
calibration calculations.
21. The method of claim 17 wherein generating a basis-point
calibrated value of the selected device parameter comprises
substituting the current raw value determined in the first zone
into a polynomial function of order n of the N-spline function
defined by the n+1 coefficients in the first zone determined in a
calibration measurement with the one or more secondary parameters
being a set of values selected to be a basis point.
22. The method of claim 17 wherein performing a multi-linear
interpolation in the first zone comprises performing M-order
multi-linear interpolation if there are M (M.gtoreq.1) number of
secondary parameters for by taking a weighted average of 2.sup.M
number of multiplicative factors at 2.sup.M number of vertices to
calculate the first adjustment multiplier, each vertex
corresponding to a set of values of the M number of secondary
parameters, each of the 2.sup.M number of multiplicative factors
being associated with a corresponding one of the multiple sets of
values of the one or more secondary parameters previously assigned
for the first zone and being stored in the non-volatile memory.
23. The method of claim 17 wherein interpolating between the first
adjustment multiplier and the second adjustment multiplier
comprises a linear interpolating between the first stating value of
the first zone and the current raw value.
24. The method of claim 17 further comprising determining the
current raw value of the selected primary parameter in a highest
zone, performing a multi-linear interpolation based on the current
set of values and alternate multiple sets of the plurality of sets
of values of the one or more secondary parameters for the highest
zone to calculate an adjustment multiplier, multiplying the
adjustment multiplier to the basis-point calibrated value to obtain
a final calibrated value of the selected device parameter to be
communicated via a data communication interface in the
microprocessor to the host.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of and claims priority to
U.S. application Ser. No. 14/860,548, filed Sep. 21, 2015, commonly
assigned and incorporated by reference herein for all purposes.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to optical module calibration
techniques. More particularly, the present invention provides a
system and method for calibrating general purpose device parameter
of an optical module. Specifically, the system and method are
implemented with control logic being fully coded in an internal
logic control unit with non-volatile memory before being applied
for the characterization of various devices within the optical
module.
[0003] In an optical module, it may not be known in advance,
especially when designing system control logic, exactly how various
internal devices will behave. For example, optical module for
network communication usually includes multiple different devices
manufactured in a high mix environment and needs to be integrated
together and operated under one internal logic control unit. The
mix of devices may change from time to time. This is particularly
true for such optical networking module to select different WDM
(wave division multiplexed) or DWDM (dense wave division
multiplexing) devices, transmitters, receivers, or transceivers, RF
modulator, subsystem for communicating to a host, and/or analog
control units, all possibly having different constructions and
being designed for different channel wavelengths. Thus, it is
inefficient to dedicate a production line or testing station to a
particular module or component. Instead, optical modules require a
calibrated version of multiple device parameters to be communicated
with the host and internal controls also require calibration in
order to function properly.
[0004] Therefore, it is desired to have improved system and method
for optical module calibration that cover various calibration
requirements with a minimum of physical memory space requirements
and with a minimum of additional overhead at the time of
calibration.
BRIEF SUMMARY OF THE INVENTION
[0005] The present invention relates to optical module calibration
techniques. More particularly, the present invention provides a
system and method for calibrating general purpose device parameter
of an optical module. The calibration system and method are applied
with control logic being fully coded in the optical module before
being applied for the characterization of various devices within
the optical module, though other applications are possible.
[0006] In a specific embodiment, the present invention provides a
method of performing calibration of a device parameter of an
optical module. The method includes providing said optical module
in a calibration station. The optical module includes an internal
logic control unit with non-volatile memory capable of measuring
raw values of a plurality of primary parameters at all operation
conditions including variations of one or more secondary parameters
adjusted by the calibration station. Further the method includes
determining N number of zones corresponding to a selected primary
parameter for calibration of said device parameter, N.gtoreq.1 and
determining an order n of a polynomial function for each of the N
zones wherein n.gtoreq.0 and is varied for the N zones.
Additionally, the method includes performing calibration
measurements for each of the N zones, in which the method includes
performing a first plurality of calibration measurements in the
selected zone, with the one or more secondary parameters being set
at corresponding values selected as a basis point, to obtain a
plurality calibrated values of the device parameter measured by a
pre-calibrated measurement equipment respectively against a
plurality of raw values of the selected primary parameter in the
selected zone measured by the optical module to deduce n+1 number
of coefficients. Further for each zone, the method includes
performing a second plurality of calibration measurements
respectively at a second plurality of calibration points to
generate a multiplicative factor of the selected zone for each
calibration point. Furthermore for each zone, the method includes
storing the n+1 number of coefficients for constructing the order n
polynomial function and the multiplicative factor associated with
each of the second plurality of calibration points for the selected
zone into the non-volatile memory. Moreover, the method includes
generating an N-spline function for all N zones based on each order
n polynomial function for each zone at the basis point. The
N-spline function is programmed into an internal logic control unit
such as a microprocessor for generating a basis-point calibrated
value of the device parameter for the optical module.
[0007] In another specific embodiment, the present invention
provides a method of delivering a calibrated device parameter of an
optical module to be communicated to a host. The method includes
providing an optical module comprising a microprocessor with
non-volatile memory capable of measuring entire value range of each
of one or more primary parameters in association with variations of
one or more secondary parameters. The microprocessor is programmed
with an internal control logic comprising at least a N-spline
function for N number of zones incrementally over the entire value
range of a selected primary parameter for generating a
corresponding calibrated value of said selected device parameter
along with the non-volatile memory being configured to store at
least a plurality of multiplicative factors respectively associated
with the plurality of sets of values of the one or more secondary
parameters for each of the N number of zones. Additionally, the
method includes measuring a current raw value of the selected
primary parameter at a current set of values of the one or more
secondary parameters. The method further includes determining the
current raw value in a first zone of the N number of zones if the
current raw value is greater than a first starting value of the
first zone and smaller than a first starting value of a second
zone. Furthermore, the method includes generating a basis-point
calibrated value of said selected device parameter based on the
current raw value using the N-spline function in the first zone.
The method further includes performing a multi-linear interpolation
based on the current set of values and multiple sets of the
plurality of sets of values of the one or more secondary parameters
for the first zone to calculate a first adjustment multiplier. The
method then includes performing a multi-linear interpolation based
on the current set of values and alternative multiple sets of the
plurality of sets of values of the one or more secondary parameters
for the second zone to calculate a second adjustment multiplier.
Furthermore, the method includes interpolating between the first
adjustment multiplier and the second adjustment multiplier to
obtain a final multiplier. Moreover, the method includes
multiplying the final multiplier to the basis-point calibrated
value to obtain a final calibrated value of the selected device
parameter to be communicated to the host.
[0008] In yet another specific embodiment, the present invention
provides a method for calibration of an optical module. The method
includes determining a device parameter of said optical module to
be calibrated against a selected primary parameter. The optical
module includes a microprocessor with non-volatile memory capable
of measuring raw values of the selected primary parameter at all
operation conditions with adjustments of one or more secondary
parameters. The method includes determining a multi-zone
calibration function of the device parameter against incrementally
sorted raw values of the selected primary parameter in multiple
zones by measuring calibrated values of the device parameter at
multiple calibration points corresponding to the selected primary
parameter being set to multiple raw values including at least a
minimum value in each zone and the one or more secondary parameters
being fixed to a set of basis-point values. Additionally, the
method includes performing additional measurements of calibrated
values of the device parameter at multiple calibration points
corresponding to the one or more secondary parameters being
adjusted to one or more sets of adjustment-point values away from
the set of basis-point values and with the selected primary
parameter being at least set to the minimum value in each zone to
obtain a multiplicative factor for each set of values of the
secondary parameters for each zone. The method further includes
generating a basis-point calibrated value of the device parameter
by using the multi-zone calibration function in a current zone of
the multiple zones found for a current raw value of the primary
parameter with the one or more secondary parameters being at a
current set of values. Furthermore, the method includes performing
multi-linear interpolation of multiple multiplicative factors based
on the current set of values and multiple sets of adjustment-point
values in both the current zone and a next higher zone to calculate
a multiplier. Moreover, the method includes multiplying the
multiplier to the basis-point calibrated value to deliver a final
calibrated value of the device parameter communicated with a
host.
[0009] In an alternative embodiment, the present invention provides
a system for calibrating a selected device parameter of an optical
module for communicating a calibrated value to a host. The system
includes an optical module including an internal logic control unit
with non-volatile memory, an Analog and Digital communication unit
configured to control all internal optical devices for measuring
raw values for a selected primary parameter sorted in multiple
zones at all operation conditions including adjustments of one or
more secondary parameters, a software embedded in the internal
logic control unit for executing a calibration operation of the
selected device parameter to deduce a calibrated value in any
current operation condition using both a multi-zone N-spline
function of the selected primary parameter in each of the multiple
zones and a multiplier associated with the one or more secondary
parameters for each zone stored in the non-volatile memory, and a
data communication interface configured to report the calibrated
value. Additionally, the system includes a calibration station
including equipment to adjust the one or more secondary parameter,
a test data communication bus connecting the host to one or more
pre-calibrated measurement equipments configured to provide
calibrated measurements of the selected device parameter, a test
data generation block for data communication between the optical
module and the host, a computer loaded with a calibration software
for assisting measurements of each primary parameter and the one or
more secondary parameters, performing logic operation in defining
the multiple zones, sorting measurement data in each zone,
calculating coefficients for generating the N-spline function for
the multiple zones, deducing multiple multiplicative factors for
multiple value vertices of the one or more secondary parameters for
each zone, storing at least the coefficients for generating the
multi-zone N-spline function and multiple multiplicative factors
into the non-volatile memory of the optical module via I2C
communication interface or other digital communication system. In
an embodiment, the calibrated value for the selected device
parameter at any current operation condition is obtained by
operating the internal logic control unit to calculate a
basis-point calibrated value using the multi-zone N-spline function
generated by the coefficients for at a particular zone of the
primary parameter corresponding to the current operation condition,
to calculate an adjustment multiplier by interpolating the multiple
multiplicative factors with corresponding weights depended on the
one or more secondary parameters at the current operation condition
with respect to at least two calibration points, and to multiply
the adjustment multiplier to the basis-point calibrated value.
[0010] The preferred calibration system and method provided in this
application is applicable for general purpose device parameter
calibration where the control logic can be fully coded before the
devices within the optical module have been characterized. An
embodiment of the present invention provides a multi-zone
calibration system capable of adjusting more than one secondary
parameters and interpolating multiple adjuster multipliers to
obtain accurate calibrated result for any selected device parameter
at any operation conditions. Embodiments of the present invention
should be applicable for performing majority of possible
calibrations of optical modules and other devices configured with a
minimum of physical memory space and with a minimum of additional
overhead at the time of calibration.
[0011] The present invention achieves these benefits and others in
the context of known waveguide laser modulation technology.
However, a further understanding of the nature and advantages of
the present invention may be realized by reference to the latter
portions of the specification and attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The following diagrams are merely examples, which should not
unduly limit the scope of the claims herein. One of ordinary skill
in the art would recognize many other variations, modifications,
and alternatives. It is also understood that the examples and
embodiments described herein are for illustrative purposes only and
that various modifications or changes in light thereof will be
suggested to persons skilled in the art and are to be included
within the spirit and purview of this process and scope of the
appended claims.
[0013] FIG. 1 is a simplified block diagram of a system for optical
module calibration for communicating to a host according to an
embodiment of the present invention.
[0014] FIG. 2 is a simplified flow of a method of performing
optical module calibration according to an embodiment of the
present invention.
[0015] FIG. 3 is an exemplary diagram for mapping raw values to
calibrated values with a high/low temperature effect over three
zones according to an embodiment of the present invention.
[0016] FIG. 4 is a simplified flowchart of a method for performing
optical module calibration by measuring and saving calibration data
according to an embodiment of the present invention.
[0017] FIG. 5 is a simplified flowchart of a method for performing
optical calibration by using calibration data to deliver calibrated
parameter according to an embodiment of the present invention.
[0018] FIG. 6 is an example data storage format used in the
internal logic control unit in the optical module for calibration
according to an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The present invention relates to optical module calibration
techniques. More particularly, the present invention provides a
system and method for calibrating general purpose device parameter
of an optical module. The calibration system and method are applied
with control logic being fully coded in the optical module before
being applied for the characterization of various devices within
the optical module, though other applications are possible.
[0020] The following description is presented to enable one of
ordinary skill in the art to make and use the invention and to
incorporate it in the context of particular applications. Various
modifications, as well as a variety of uses in different
applications will be readily apparent to those skilled in the art,
and the general principles defined herein may be applied to a wide
range of embodiments. Thus, the present invention is not intended
to be limited to the embodiments presented, but is to be accorded
the widest scope consistent with the principles and novel features
disclosed herein.
[0021] In the following detailed description, numerous specific
details are set forth in order to provide a more thorough
understanding of the present invention. However, it will be
apparent to one skilled in the art that the present invention may
be practiced without necessarily being limited to these specific
details. In other instances, well-known structures and devices are
shown in block diagram form, rather than in detail, in order to
avoid obscuring the present invention.
[0022] The reader's attention is directed to all papers and
documents which are filed concurrently with this specification and
which are open to public inspection with this specification, and
the contents of all such papers and documents are incorporated
herein by reference. All the features disclosed in this
specification, (including any accompanying claims, abstract, and
drawings) may be replaced by alternative features serving the same,
equivalent or similar purpose, unless expressly stated otherwise.
Thus, unless expressly stated otherwise, each feature disclosed is
one example only of a generic series of equivalent or similar
features.
[0023] Furthermore, any element in a claim that does not explicitly
state "means for" performing a specified function, or "step for"
performing a specific function, is not to be interpreted as a
"means" or "step" clause as specified in 35 U.S.C. Section 112,
Paragraph 6. In particular, the use of "step of" or "act of" in the
Claims herein is not intended to invoke the provisions of 35 U.S.C.
112, Paragraph 6.
[0024] Please note, if used, the labels left, right, front, back,
top, bottom, forward, reverse, clockwise and counter clockwise have
been used for convenience purposes only and are not intended to
imply any particular fixed direction. Instead, they are used to
reflect relative locations and/or directions between various
portions of an object.
[0025] FIG. 1 is a simplified block diagram of a system for optical
module calibration for communicating to a host according to an
embodiment of the present invention. This diagram is merely an
example, which should not unduly limit the scope of the claims. One
of ordinary skill in the art would recognize many variations,
alternatives, and modifications. As shown, a calibration system
1000 includes an optical module 1100 containing a microprocessor
1110 or other logical control system with non-volatile memory, an
analog and digital communication interface 1120 coupled to the
microprocessor 1110 and several internal optical devices including
an optical transmit circuitry 1140 comprising laser with TEC and RF
driver, an optical receive circuitry 1150 comprising photo detector
and TIA device, and a multi-channel mux/demux device (not
specifically shown). Also the optical module 1100 includes a data
communication interface 1130 configured to couple to both the
optical transmit circuitry 1140 and optical receive circuitry 1150
and to an external test data generation block 1300 (as an outside
host).
[0026] The microprocessor 1110 is preloaded or encoded with
software configured for the optical module calibration. In an
embodiment, it contains calibration control logic with command that
can be passed via the analog and digital communication interface
1120 to the corresponding internal optical devices for measuring
raw values of any selected parameters. The measurement results can
be stored at least temporarily in the non-volatile memory of the
microprocessor 1120 and reported to a host computer (for example,
in a calibration station) via I2C communication interface or other
digital communication system and used for calibrating a device
parameter selected for communicating to a host. The software
embedded in the microprocessor 1120 is configured to execute a
calibration method disclosed in this application with description
throughout the specification. Briefly, the calibration method
includes generating a multi-zone N-spline function of the selected
primary parameter in each zone to deduce a basis-point calibration
value of a device parameter selected for calibration and
determining a multiplier associated with the one or more secondary
parameters for the basis point and at least another calibration
point for each zone. The final calibrated value can be obtained by
multiplying the determined multiplier and communicated to the host
computer via the I2C communication interface or other digital
communication system and a data communication interface configured
to report the calibrated value operation to deduce a calibrated
value in each calibration point.
[0027] In a specific embodiment, the calibration system includes a
calibration station comprising a pre-calibrated measurement
equipment 1200, a computer 1400 loaded with a calibration software
and a test data generation block 1300 all coupled to a test data
communication bus 1500 for communicating with external host. The
calibration station is configured to adjust environmental
conditions, e.g., temperature and voltage, which are used as
typical secondary parameters for performing the calibration
operation at a plurality of calibration points. The pre-calibrated
measurement equipment 1200 is configured to provide calibrated
measurements for the selected device parameter of the optical
module via an optical splitter to couple with the mux/demux device
of the optical module 1100 at the plurality of calibration points.
The calibration software is loaded with the aid of the computer
1400 for assisting parameter (primary and secondary) adjustment and
measurements of the primary/secondary parameters (by provide
command instruction to the microprocessor 1110 in the optical
module 1100. The calibration software also performs logic operation
in defining zones for the selected primary parameter, sorting data
in each zone, assigning different polynomials for each zone based
on its influential behavior to the to-be-calibrated device
parameter. Additionally, in the computer 1200, all calibration
calculations are performed to generate the multi-zone N-spline
function coefficients for deducing a basis-point calibrated value
and multiple multiplicative factors associated with multiple
vertices of the secondary parameter values for each zone.
Furthermore, the computer 1200 communicates the microprocessor 1110
via I2C communication interface or other digital communication
system to store the calculated calibration results into the
non-volatile memory of the optical module.
[0028] FIG. 2 is a simplified flow of a method of performing
optical module calibration according to an embodiment of the
present invention. This diagram is merely an example, which should
not unduly limit the scope of the claims. One of ordinary skill in
the art would recognize many variations, alternatives, and
modifications. As shown, the method 2000 of performing optical
module calibration starts with a step 2020 of determining
calibration parameters. This step includes determining which device
parameter is selected for calibration against which one or more
other device parameters or environmental parameters.
[0029] In an embodiment, the device parameter of the optical module
selected for calibration includes optical power including
internally generated power from a laser source and externally
transmitted or received power, optical modulation amplitude for
both transmitted and received signal, laser frequency/wavelength
per channel and wavelength shift from a target value, module
temperature, power supply voltage, optical bias current, and
thermo-electric cooler current. Among all these parameters, at
least one is also selected to be a primary parameter for
calibration the selected device parameter. In a specific
embodiment, the primary parameter can even be the same as the
target device parameter for calibration. In general the primary
parameter is selected for it is believed to have a major influence
to the device parameter so that the calibration of the device
parameter is meaningful. In another specific embodiment,
determining the primary parameter includes determining a number of
zones in terms of its value over entire range for the operation of
the optical module. This step can be done based on common knowledge
or empirical measurements of raw values of the selected primary
parameter during actual calibration process. The number of zones
determined is different from a primary parameter to another and may
also be different for a same primary parameter but when a different
device parameter is selected for calibration, all dependent on the
response behavior of the device parameter upon the selected primary
parameter.
[0030] Any calibrated parameter will have a raw value and a
calibrated value. The relationship between these two values may be
complex. It is possible that multiple raw values may be combined to
produce a single calibrated value. For the simplest case, where a
single raw value leads to a calibrated value, the behavior may be
complex. At low values of the raw parameter the relationship may be
quite different vs. at high values of the raw parameter. To
accommodate this, the raw value is split up among various zones. A
zone is a section of the curve converting the raw value to a
calibrated value.
[0031] The reason to determine multiple zones for the primary
parameter is to provide more accurate calibration of the device
parameter by assigning different polynomial mapping function for
different zone. If the number of zones is determined sufficiently
well, each zone will contain a well behaved polynomial of a certain
order. In most cases a 3.sup.rd order polynomial would be
sufficient, and in many cases a 1.sup.st order polynomial would
suffice. There is of course a trade-off between more zones and
higher order polynomial to improve accuracy. For a more complex
case, the zone may include more than one raw parameter. For the
case of two raw parameters combining to form a single calibrated
parameter, the calibrated result would be a surface. In general if
N raw parameters are required, then an N-dimensional object will
result.
[0032] In addition to whichever raw parameters are required to
determine a calibrated result; there are often environmental
conditions (e.g., system temperature or voltage) that affect the
calibration. Usually, these effects are relatively small compared
with the effect of the primary raw parameter(s). However, in order
to generate a higher level of accuracy, these secondary effects
must be taken into account. In another embodiment, the step 2020
also includes determining one or more secondary parameters that may
cause perturbation to the selected device parameter at least
providing different effects at different range of primary
parameter. For example, a module temperature determined by the
environment of the optical module may cause the selected device
parameter to change with respect to the selected primary parameter
quite differently at low temperature versus at high temperature.
Although mainly those environmental parameters like temperature or
operation power-supply voltage are selected to be the secondary
parameters, theoretically all parameters mentioned above that are
used as device parameter or primary parameter can also be selected
as secondary parameters in certain calibration according to the
present invention.
[0033] Further, the method 2000 includes a step 2030 for performing
optical module calibration by measuring the parameter response.
Specifically, the step 2030 includes performing a calibration
process to determine the mapping function to get the calibrated
result. This process requires a calibrated measuring equipment to
measure the selected device parameter at various raw values of the
primary parameters and at different calibration points associated
with varied secondary parameter values. The measurements of the raw
values of the primary parameters are carried by the optical module.
The variation of the secondary parameter can be done using
equipment in a calibration station designated for calibrating the
optical module. In an embodiment, a plurality of measurements on
the raw values of the primary parameter in each determined zone
includes at least the measurement of a starting minimum raw value
in each zone with the secondary parameters being set at a typical
(or selected as basis point) calibration point.
[0034] In another embodiment, the plurality of measurements on the
raw values at least should be sufficient for determining all
coefficients for constructing the polynomial function of certain
order in corresponding zone. For a simple one primary parameter
case, the polynomial function is a 1-dimensional function. An order
n (n.gtoreq.0) polynomial function needs n+1 coefficients. For more
complex case with two primary parameters, a 2-dimensional
polynomial function needs to be constructed with potentially more
coefficients to be determined by performing more raw-value
measurements.
[0035] In an alternative embodiment, performing measurements of the
secondary parameter values in step 2030 include setting the basis
point as well as at least one more alternate calibration point,
along with the measurement of primary parameter at the starting
minimum raw value in each zone (by the optical module) and a
corresponding measurement of calibrated value of the selected
device parameter against this starting minimum raw value (by the
pre-calibrated measurement equipment). The secondary parameter is
adjusted by the calibration station where the optical module is
disposed for calibration. Typically, by common sense, the
adjustment of the secondary parameter is intended to cover the
widest range of the secondary parameter itself during the operation
of the optical module by design so that the affection of the
secondary parameters on the calibration of the selected device
parameter can be taken account with full extent.
[0036] In the present invention, the secondary effects are handled
by including them as a multiplicative factor onto the primary
result. One or more secondary parameters may have an impact on the
calibration. The multiplicative factor must be determined by
performing the device calibration at various environmental points
in addition at the zone calibration points. The multiplicative
factor may itself be a complex function of these one or more
secondary parameters. The algorithm handles this by employing a
multi-stage interpolation process to determine the most appropriate
multiplier to use together with the primary calibration function
response. In a specific embodiment, the measurements of the
secondary parameters at various calibration points are performed
for each zone of primary parameter to provide a multiplicative
factor per each value vertex of the secondary parameters at each
calibration point. In general, for one secondary parameter, at
least two vertices (i.e., two separate values) are needed; for two
secondary parameters, at least four vertices (of four calibration
points) are needed; for M number of secondary parameters, at least
2.sup.M vertices (of four calibration points) are needed for
correspondingly determining 2.sup.M number of multiplicative
factors for each zone.
[0037] Further, the method 2000 includes a step 2040 of delivering
calibrated parameter value for all operation conditions of the
optical module. Once the multi-zone mapping function is determined
by the coefficients of corresponding polynomials in respective
zones, the data including these coefficients, all multiplicative
factors, and all values of secondary parameters at various
calibration points for each zone of the primary parameter can be
saved into a non-volatile memory in a microprocessor or other logic
control unit of the optical module. The microprocessor can execute
an embedded software code to use the saved coefficients to
construct a mapping function for a particular zone based on any
current raw value of the primary parameter measured by the optical
module at any current operation condition to calculate a
basis-point calibrated value of the device parameter. Additionally,
the current secondary parameter values (corresponding to the
current operation condition) can be used to perform an
interpolation operation utilizing the stored multiplicative factors
and all secondary parameter values at corresponding calibration
points for the particular zone to calculate a final multiplier
representing all the effect of the secondary parameter at current
operation condition on the calibrated value of the device
parameter. The method ends at step 2050, wherein the calibrated
value may be communicated to an external host of the optical
module.
[0038] FIG. 3 is an exemplary diagram for mapping raw values to
calibrated values with a high/low temperature effect over three
zones according to an embodiment of the present invention. This
diagram is merely an example, which should not unduly limit the
scope of the claims. One of ordinary skill in the art would
recognize many variations, alternatives, and modifications. As
shown, a primary parameter with an S-shaped conversion from raw
values to calibrated values, with a high temperature effect at low
values and a low temperature affect at high values. Note, all
calibrated values and raw values plotted in the graph of FIG. 3
have been converted to a proper numerical unit from original
measurement data with different physical units. There are three
clear zones of behavior with the center zone, marked as a box,
being relatively linear and the two outside zones (not marked)
could be represented by a cubic polynomial function. In addition,
the secondary affects must also be taken into account and are
different in the three zones. In the first zone to the left, the
effect of low value(s) of the secondary parameter (the temperature
in this example) on the calibrated values is substantially
negligible. But the effect of high value(s) of the secondary
parameter on the calibrated values is quite strong, causing up to
50% increase in the calibrated value for the same raw value of the
primary parameter. Contrary to that, in the third zone to the
right, the effect of low value(s) of the secondary parameter on the
calibrated values is strong. The example shows that using multiple
zones for the calibration against the primary parameter also needs
to handle the secondary parameter effects differently in different
zone, which is achieved by embodiments of the present
invention.
[0039] In the example, although there are 3 zones of interest, a
4.sup.th zone is named theoretically to merely provide a maximum
value of the primary parameter. In this graph, the raw value of the
primary parameter is plotted in a sorted order from smaller value
to larger value. Although the real situation could be more complex,
the calibrated values in this example are also increased
accordingly. Based on the response behavior, different mapping
polynomial function of certain order may be assigned for each zone.
In Zone 1, the starting point of raw value is 0 with a polynomial
function of order 3 being assigned. The temperature is selected to
be a secondary parameter with at least two measurement points: 25
and 70 (.degree. C.). In Zone 2, the starting point of raw value is
25000 with a polynomial of order 1 being assigned. The secondary
parameter, temperature, is measured at 0, 25, and 70. In Zone 3,
the starting point is 37500. Polynomial function of order 3 is
assigned and the secondary parameter measurement points are 0 and
25. Zone 4 is merely a single point, also a starting point, at
57600 as a constant so a polynomial of order 0 is provided. Again,
the secondary parameter measurement points include 0 and 25.
[0040] FIG. 4 is a simplified flowchart of a method for performing
optical module calibration by measuring and saving calibration data
according to an embodiment of the present invention. This diagram
is merely an example, which should not unduly limit the scope of
the claims. One of ordinary skill in the art would recognize many
variations, alternatives, and modifications. As shown, the method
4000 for performing optical module calibration starts with a step
4010 of determining at least a primary parameter, a number of
zones, and an order of polynomial for each zone. This step is
substantially similar to the step 2020 of the method 2000 disclosed
in FIG. 2 of this specification. For multiple primary parameters,
each primary parameter is determined to be split to different
number of zones depending on its nature and relationship with the
device parameter selected for calibration. In each zone, a
2-dimensional polynomial function is provided to be determined as a
mapping function of the zone. This step also includes determining
one or more secondary parameters for dealing their affections on
the device parameter selected for calibration. This step is
followed by a step 4020 for determining a set of values of the one
or more secondary parameters as a basis point for the calibration
measurements.
[0041] Once the list of parameters, the number of multiple zones,
and the order of the polynomials for each zone is determined, a
calibration process is run to determine the mapping function to get
the calibrated result for the selected device parameter of the
optical module. This process requires a calibrated measuring
equipment to measure the calibrated value of the selected device
parameter against each raw value of the primary parameter measured
by the optical module. The method 4000 moves to a step 4030 of
performing calibration measurements for each of the multiple zones.
The operation for each zone can be performed in parallel or in
series depending on the layout of calibration station with a
pre-calibrated measurement equipment and corresponding calibration
software loaded with the computer associated with the calibration
station as well as coded in a microprocessor or other logic control
unit of the optical module.
[0042] For each zone, the calibration measurement is performed in a
series of steps starting with a step 4110 of measuring raw values
of the primary parameter from a minimum through a selected zone. In
the step 4110, raw values of the primary parameter in the selected
zone is firstly measured by the optical module with the one or more
secondary parameters being set at corresponding values selected as
a basis point. In particular, multiple raw values are selected in
different measurements including at least a starting minimum value
in the selected zone. In an embodiment, the measurements of raw
values of the primary parameter are done by internal optical
devices of the optical module controlled via an analog/digital
communication interface using a control logic loaded in the
microprocessor or the logic control unit. The number of raw value
measurements depends on a target mapping function assigned for the
selected zone. In order to determine all n+1 coefficients required
for constructing a n-order polynomial function assigned for a
particular zone, n+1 number of measurements are at least performed,
where n.gtoreq.0. Other than the minimum value of the selected zone
is measured, a minimum value of next higher zone is also selected
for measuring. One or more intermediate raw values are then
selected depending on specific zone with corresponding polynomial
function.
[0043] Following the step 4110 for each raw value measurement, a
step 4120 is performed to measure calibrated values of the device
parameter by the pre-calibrated measurement equipment. After each
measurement of the raw value and corresponding calibrated value, a
unit conversion is performed to convert either the measured raw
value or the calibrated value from its original physical unit to a
pure numerical unit for all subsequent calibration calculations.
Combining all measurement data from step 4110 and step 4120, all
coefficients for constructing a mapping polynomial function of the
selected zone can be deduced, with the one or more secondary
parameters being set at corresponding values selected as a basis
point.
[0044] Additionally in step 4130, for each selected zone, more
measurements on the calibrated values of the device parameter are
performed corresponding to the raw value at the minimum value of
the selected zone but with the one or more secondary parameters
being adjusted to different values corresponding to one or more
calibration points alternate to the basis point. Following each
step 4130, another step 4140 is performed to convert the measured
calibrated values in step 4130 to a multiplicative factor by taking
ratio of the calibrated value at each alternate calibration point
over the calibrated value at the basis point (obtained in step
4120). Depending on the number of secondary parameters used for the
calibration, a minimum number of measurements in step 4130 at
different calibration points (plus the one for the basis point) is
needed so that a multiple multiplicative factor are obtained
corresponding to each calibration point. Namely, at the basis
point, the multiplicative factor is 1. At other calibration points,
the multiplicative can be greater or smaller than 1.
[0045] In an embodiment, after completing all measurements and
calculations in the step 4030 for each zone of the multiple zones,
the method 4000 moves to next step 4040 of generating a N-spline
function for mapping the calibrated value against the primary
parameter for all zones corresponding to a basis point of the one
or more secondary parameters. In particular, the N-spline function
is a multi-sectional continuous function that combines all
polynomial functions in corresponding zones with some restrictions
imposed. For example, for a zone with a polynomial of order n=1,
this will be a piecewise linear curve to simply connect with a
function of next zone. For a zone with a polynomial function of
order n=3, this will be a cubic spline. The connection with next
zone needs to set respective 1st and 2nd derivative to be constant
at zone boundaries in addition to the connection of the two
boundary points which is essentially one point because the maximum
value point of the selected zone actually is the minimum value
point of next higher zone.
[0046] In a specific embodiment, for the first and last zone,
special consideration may be needed to determine the best
coefficients. In addition, if higher-order (n>1) polynomials are
used, and then intermediate points within the zone will be needed
to determine the correct coefficients for constructing the order n
polynomial function. Finally, additional intermediate points may be
used to provide a statistical determination of the coefficients
(using a polynomial fitting algorithm, such as a least squares
fit). Note that the last zone may require additional calibration
points if it has order >0.
[0047] In a specific embodiment, the first waveguide 373 in the
integrated two-channel spectral combiner and wavelength locker 350
is made longer than the second waveguide 374 by a predetermined
length which provides a delayed phase shift to the optical signals
traveling in the first waveguide 373. In other words, a delay-line
interferometer is formed with the two waveguide paths having
different lengths. When the two halves of optical signals (having
the same wavelength) meet again in the output MIMI coupler 342,
this delayed phase shift, if properly tuned, would lead to an
interference spectrum with enhanced passbands at particular phases.
This applies to both optical signals .lamda.1 and .lamda.2.
[0048] Table 1 shows an example of measurements of calibrated
values against a primary parameter from corresponding minimum value
in each of 4 zones and at several calibration points including a
basis point of a secondary parameter. This table is based on the
exemplary relationship between the calibrated value and the raw
value shown in FIG. 3.
TABLE-US-00001 TABLE 1 Raw Secondary Unit-converted starting
parameter Calibrated Zone point point value Value 1 0 25 10543 1 0
70 14760 2 25000 0 22230 2 25000 25 23399 2 25000 70 24569 3 37500
0 35520 3 37500 25 39467 4 57600 0 44315 4 57600 25 49239
[0049] Based on Table 1 and the method 4000 of FIG. 4, multipliers
associated with several adjustment points for each zone are
generated and shown in Table 2 below.
TABLE-US-00002 TABLE 2 Secondary parameter Zone point value
Multiplier Determined by 1 25 1 Basis point 1 70 1.40 Zone 1 70
C/Zone 1 25 C 2 0 0.95 Zone 2 0 C/Zone 2 25 C 2 25 1 Basis point 2
70 1.05 Zone 2 70 C/Zone 2 25 C 3 0 0.90 Zone 3 0 C/Zone 3 25 C 3
25 1 Basis point 4 0 0.90 Zone 4 0 C/Zone 4 25 C 4 25 1 Basis
point
[0050] Finally, based on the Table 1 and Table 2 above, all the
polynomial coefficients at the basis point (25 C) for each zone can
be generated using the method 4000 proposed in FIG. 4. The results
are shown below in Table 3 with the determination detail
methodology shown in last column.
TABLE-US-00003 TABLE 3 Coef. Zone # Coef. Value Determined by: 1 0
10543 Cubic calculated from 4 equations: 1 1 0.12864 y" (zone 1 raw
start) = 0 1 2 0 y' (zone 2 raw start) = y' (zone 2 1 3 6.1696E-10
linear calculation below) (x1, y1) = zone 1 raw start, zone 1 raw
start 25 C calibrated value (x2, y2) = zone 2 raw start, zone 2 raw
start 25 C calibrated value 2 0 -8737 Line calculated from 2
points: 2 1 1.285 (x1, y1) = zone 2 raw start, zone 2 raw start 25
C calibrated value (x2, y2) = zone 3 raw start, zone 3 raw start 25
C calibrated value 3 0 -122066.88 Cubic calculated from 4
equations: 3 1 8.32641365 Y" (zone 4 raw start) = 0 3 2 -0.0001337
y' (zone 3 raw start) = y' (zone 2 linear 3 3 7.0877E-10
calculation above) (x1, y1) = zone 3 raw start, zone 3 raw start 25
C calibrated value (x2, y2) = zone 4 raw start, zone 4 raw start 25
C calibrated value 4 0 49239 y0 = zone 4 raw start 25 C calibrated
value Note: y" is 2.sup.nd derivative quantity, y' is 1.sup.st
derivative quantity, y0 is constant.
The data in the tables above are stored into non-volatile memory of
the device under test to be used during operation to provide a
calibrated result. The data must be sorted such that the lower raw
values are stored first in the memory and the secondary parameters
must always be presented in the same order. A storage structure
stored in the internal logic control unit is proposed as an example
below in FIG. 6, which is sufficiently self-explanatory.
[0051] FIG. 5 is a simplified flowchart of a method for performing
optical calibration by using calibration data to deliver calibrated
parameter according to an embodiment of the present invention. This
diagram is merely an example, which should not unduly limit the
scope of the claims. One of ordinary skill in the art would
recognize many variations, alternatives, and modifications. As
shown, a method 5000 for performing optical calibration by using
calibration data to deliver calibrated parameter is performed on an
arbitrary operation condition of the optical module. The method
5000 starts with step 5010 of measuring a current raw value (r) of
the primary parameter of the optical module at a set of current
values of one or more secondary parameters. The current raw value
of the primary parameter and the current set of values of the one
or more secondary parameters are part of the current operation
condition measured by the optical module. Based on the measured
current raw value in step 5010, step 5020 is to determine the
currently measured raw value in one particular zone of multiple
zones (e.g., the multiple zones determined in step 4010 of method
4000). In an embodiment, if the starting point (r0) of the
particular zone is below the currently measured raw value, the
current raw value belongs to the particular zone. For the
convenience of description, the particular zone is the first
zone.
[0052] In an embodiment, the method 5000 is executed within the
optical module itself including a microprocessor or other logic
control system programmed with a calibration software based on a
multi-zone N-spline mapping function defined by the method 4000
with all coefficients stored in an associated non-volatile memory
along with all multiplicative factors and all sets of values of the
secondary parameters corresponding to various calibration points.
Therefore, the method 5000 moves to step 5030 to use a particular
order n polynomial function corresponding to the particular zone
determined in step 5020 to calculate a basis-point calibrated
value. This is done by simply substituting the current raw value
into the order n polynomial functions constructed by the stored
coefficients. For example, the basis-point calibrated value (p) is
obtained using the N polynomial coefficients (C.sub.n) for the
matching zone:
p = n = 0 N C n r n ##EQU00001##
[0053] In an specific embodiment, the non-volatile memory of the
microprocessor in the optical module is also configured to save all
the multiplicative factors obtained during a plurality of
calibration measurements on the optical module, per each zone of
primary parameter, at corresponding various calibration points with
the one or more secondary parameters being at the various sets of
values. In next step 5040 of the method 5000, these data stored in
the non-volatile memory will be utilized for performing a
multi-linear interpolation calculation for the particular zone
(determined in step 5020) on the multiple multiplicative factors to
deduce a multiplier for the zone. The interpolation calculation is
based on the secondary parameter values at the current operation
condition with respect to the corresponding sets of values
associated with the determination of the multiple multiplicative
factors at corresponding multiple calibration points (e.g.,
performed in step 4140 of method 4000) for the particular zone.
[0054] Each secondary parameter corresponds to an adjuster (for the
calibration of the device parameter). Each adjuster will have a
current value determined by current measurement, as well as a set
of measurement values determined at corresponding calibration
points (e.g., when performing step 4140). For each adjuster, if the
current value lies between two measurement values corresponding to
two calibration points then those two points can be used as
vertices in the multi-linear interpolation. If the current value
lies below the lowest or above the highest measurement values then
there are two options: 1) assume a constant value (i.e., extend the
lowest/highest value), or 2) assume a linear continuation of the
highest/lowest two points. In either case, for each adjuster there
will be two interpolation points. For each vertex of interpolation
points a multiplicative factor M is associated with.
[0055] With a single adjuster, this is reduced to a simple linear
interpolation of the measured secondary parameter value (A) between
the two measurements corresponding to two calibration points
(A.sub.0, A.sub.1) respective associated with two multiplicative
factors M(A.sub.0) and M(A.sub.1), leading to an adjustment
multiplier m.sub.0 for the particular zone:
m 0 = ( A 1 - A ) M ( A 0 ) + ( A - A 0 ) M ( A 1 ) ( A 1 - A 0 )
##EQU00002##
[0056] With two adjusters, then there will be 4 vertices: {A.sub.0,
B.sub.0}, {A.sub.1, B.sub.0}, {A.sub.0, B.sub.1} and {A.sub.1,
B.sub.1} each vertex having a multiplicative factor M. The current
value of parameter A and B can be described as a vector with the
value {A, B}. In this case, a rectangular interpolation is used to
lead to an adjustment multiplier m.sub.0 for the particular zone,
as follows:
m 0 = ( A 1 - A ) ( B 1 - B ) M ( A 0 , B 0 ) + ( A - A 0 ) ( B 1 -
B ) M ( A 1 , B 0 ) + ( A 1 - A ) ( B - B 0 ) M ( A 0 , B 1 ) + ( A
- A 0 ) ( B - B 0 ) M ( A 1 , B 1 ) ( A 1 - A 0 ) ( B 1 - B 0 )
##EQU00003##
[0057] For higher orders, an N-order multi-linear interpolation is
calculated by taking a weighted average of the multiplicative
factors Mat the 2.sup.N vertices. The weights are determined via a
geometric conception where the weight of a particular vertex is
proportional to the geometric N-volume of the region bounded by the
current parameter value vector and the diametrically opposite
vertex, expressed as a fraction of the total N-volume bounded by
all the vertices. For performing the above interpolation
calculations, the data storage requirements in the non-volatile
memory of the microprocessor should be capable of storing all
secondary adjusters associated with each zone of the primary
parameter, including values of all secondary parameters in all
calibration points and all multiplicative factors deduced at all
calibration points. For example, with 4 adjusters having 3, 5, 7,
and 2 calibration points respectively, there will be 3+5+7+2=17
total measurement values and additional
3.times.5.times.7.times.2=210 total multiplicative factors stored
in the non-volatile memory of the optical module.
[0058] In another embodiment, the method 5000 moves to step 5050,
if the current raw value is not falling into the last zone with the
highest value, to perform another a multi-linear interpolation
calculation for a next higher zone (determined in step 5020) on the
multiple multiplicative factors to deduce a multiplier for that
zone. The interpolation calculation is based on the secondary
parameter values at the current operation condition with respect to
the corresponding sets of values associated with the determination
of the multiple multiplicative factors at multiple corresponding
calibration points (e.g., performed in step 4140 of method 4000)
for the particular zone. In the end, another adjustment multiplier
m.sub.1 is obtained for the next higher zone.
[0059] Referring to FIG. 5, the method 5000 now includes a step
5060 to interpolate the results in both step 5040 and step 5050.
Once the adjustment multiplier (m.sub.0) has been calculated for
the particular matching zone, and also for the next higher zone
(m.sub.1), the resulting pair of adjustment multipliers is used to
do a final interpolation along the axis of the original raw
parameter (r) to determine a final multiplier m:
m = m 0 + m 1 - m 0 r 1 - r 0 ( r - r 0 ) ##EQU00004##
[0060] The method 5000 includes a step 5070 for multiplying the
final multiplier m to the basis-point calibrated value (p) to
obtain a final calibrated value (f) of the device parameter of the
optical module:
f=m p
[0061] While the above is a full description of the specific
embodiments, various modifications, alternative constructions and
equivalents may be used. Therefore, the above description and
illustrations should not be taken as limiting the scope of the
present invention which is defined by the appended claims.
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