U.S. patent application number 14/522409 was filed with the patent office on 2016-04-28 for burst-mode laser control circuit and the method thereof.
This patent application is currently assigned to SOURCE PHOTONICS (CHENGDU) CO., LTD.. The applicant listed for this patent is Xu JIANG, Yuan SONG, Yuanzhong XU, Shuyuan ZHANG. Invention is credited to Xu JIANG, Yuan SONG, Yuanzhong XU, Shuyuan ZHANG.
Application Number | 20160119061 14/522409 |
Document ID | / |
Family ID | 53127902 |
Filed Date | 2016-04-28 |
United States Patent
Application |
20160119061 |
Kind Code |
A1 |
JIANG; Xu ; et al. |
April 28, 2016 |
Burst-Mode Laser Control Circuit and the Method Thereof
Abstract
A burst-mode laser control circuit and related methods thereof
are disclosed. Using an APC loop with an additional burst-mode
control circuit, and a switch in series with a diode and in
parallel with the laser, a continuous-mode laser driver is enabled
to operate in burst-mode by turning the switch on or off via
external logic. Burst-mode control manages the switch, and a
bandwidth-select circuit using a high or low logic level input,
wherein the laser is disabled and the bandwidth-select circuit
enters a fast-track mode when the external logic signal has a first
level. The laser provides regular optical signals, and the
bandwidth-select circuit enters a slow-track mode, thereby enabling
the APC loop to operate normally, when the external logic signal
has a second level. In addition to a low cost and simple
implementation, the control circuit and method provide lasers with
a fast response capability using one or more externally-controlled
switch circuits to meet demands of PON systems for burst-mode
ONUs.
Inventors: |
JIANG; Xu; (Chengdu, CN)
; SONG; Yuan; (Chengdu, CN) ; ZHANG; Shuyuan;
(Chengdu, CN) ; XU; Yuanzhong; (Chengdu,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JIANG; Xu
SONG; Yuan
ZHANG; Shuyuan
XU; Yuanzhong |
Chengdu
Chengdu
Chengdu
Chengdu |
|
CN
CN
CN
CN |
|
|
Assignee: |
SOURCE PHOTONICS (CHENGDU) CO.,
LTD.
Chengdu
CN
|
Family ID: |
53127902 |
Appl. No.: |
14/522409 |
Filed: |
October 23, 2014 |
Current U.S.
Class: |
398/182 |
Current CPC
Class: |
H04B 10/272 20130101;
H04B 10/503 20130101; H01S 5/06832 20130101; H01S 5/12 20130101;
H04B 10/564 20130101 |
International
Class: |
H04B 10/50 20060101
H04B010/50; H04B 10/564 20060101 H04B010/564 |
Claims
1-7. (canceled)
8. A burst-mode laser control circuit, comprising: a) an automatic
power control (APC) loop; b) a laser; c) a diode; and d) a
burst-mode control circuit comprising a switch in series with the
diode and parallel to the laser, the switch being enabled or
disabled by external logic, thereby providing burst-mode control of
the laser.
9. The burst-mode laser control circuit of claim 8, wherein said
switch and said bandwidth-select circuit are enabled or disabled
with a high or low logic level input.
10. The burst-mode laser control circuit of claim 9, wherein said
bandwidth-select circuit comprises a high-low bandwidth-select
circuit and a delay circuit.
11. The burst-mode laser control circuit of claim 10, wherein said
high-low bandwidth-select circuit comprises has a fast-track mode
and a slow-track mode.
12. The burst-mode laser control circuit of claim 11, wherein said
switch disables the diode and the bandwidth-select circuit enters
fast-track mode when the external logic provides a high logic
level, and the laser provides optical signals and the
bandwidth-select circuit enters a slow-track mode when the external
logic provides a low logic level.
13. The burst-mode laser control circuit of claim 11, wherein said
delay circuit comprises delay control logic configured to operate
the APC loop in the fast-track mode before enabling the laser, and
operate the APC loop in the slow-track when enabling the laser to
operate.
14. The burst-mode laser control circuit of claim 13, wherein said
delay control logic enables the APC loop to control power to the
laser before the laser is enabled, thereby providing a stable laser
power output when the laser begins to operate.
15. The burst-mode laser control circuit of claim 8, wherein the
APC loop comprises the laser, a continuous-mode laser driver, and
the bandwidth-select circuit.
16. The burst-mode laser control circuit of claim 8, wherein the
laser comprises a burst mode laser.
17. The burst-mode laser control circuit of claim 16, wherein the
burst mode laser comprises a distributed feedback (DFB) laser or an
electro-amplitude modulated laser (EML).
18. The burst-mode laser control circuit of claim 16, further
comprising a continuous mode laser driver, receiving a control
signal from the APC loop and providing a driving signal to the
laser.
19. A method of controlling a laser having a burst mode,
comprising: a) when a logic input to an optical network unit (ONU)
in a passive optical network (PON) has a first logic state, placing
a bandwidth-select circuit in a fast-track mode for a predetermined
period of time and disconnecting a switch, the ONU including the
switch, a laser, a laser driver, a diode and the bandwidth-select
circuit; b) after the predetermined period of time, driving the
laser using the laser driver and transmitting an optical signal
from the laser normally; c) when the optical signal from the laser
is stable, placing the bandwidth-select circuit in a slow-track
mode; d) when the logic input to the ONU has a second state,
turning on the switch to disable the optical signal from the laser
and connect the laser in parallel with the diode; and e) placing
the bandwidth-select circuit in the fast-track mode when the logic
input has the first logic state again.
20. The method of claim 19, wherein the first logic state is a low
logic level, and the second logic state is a high logic level.
21. The method of claim 19, wherein the predetermined period of
time is about 20 ns.
22. The method of claim 19, wherein after said logic input
transitions to the second state, the bandwidth-select circuit stays
in the fast-track mode for the predetermined period of time.
23. The method of claim 19, wherein placing the bandwidth-select
circuit in the slow-track mode keeps optical signals from the laser
stable.
24. The method of claim 19, wherein decreasing a voltage/current at
a cathode and an anode of the laser results in no optical signal
from the laser.
Description
FIELD OF THE INVENTION
[0001] This invention relates to the field of laser devices,
especially to burst-mode laser control circuits and methods
pertaining thereto.
DISCUSSION OF THE BACKGROUND
[0002] In conventional burst-mode laser driver circuits, laser
devices generally do not operate in burst-mode without burst-mode
laser drivers. However, with regard to 10G or higher speed laser
devices, such as DFB (Distributed Feedback) laser devices Laser) or
EML (Electro-absorption Modulated Laser) devices, there are only
continuous-mode laser drivers. With the development of 10G PON
(Passive Optical Network) applications, ONU (Optical Network Unit)
products supporting 10G or higher speeds are needed to meet the
demands of PON systems for burst-mode operation.
SUMMARY OF THE INVENTION
[0003] This invention provides a burst-mode laser control circuit
and a method of improved burst-mode control for laser devices. The
technical solution(s) are as follows: a burst-mode laser control
circuit with an APC loop, having an additional burst-mode control
circuit; the burst-mode control circuit comprising a switch in
series with a diode and in parallel with the laser, enabled or
disabled by external logic, to thereby provide burst-mode control
for laser devices (e.g., continuous mode lasers).
[0004] The switch and the bandwidth-select circuit may be
controlled by a high or low logic level input from the external
logic.
[0005] The bandwidth-select circuit may comprise or consist of two
functional circuits: a high-low bandwidth-select circuit and a
delay circuit.
[0006] The high-low bandwidth-select circuit has at least two
modes: a fast-track mode and a slow-track mode.
[0007] When the external logic controls the switch and
bandwidth-select circuit via a high or low logic level input, the
laser is disabled and the bandwidth-select circuit enters the
fast-track mode when a high logic level is inputted (e.g., applied
to the switch); and the laser provides regular optical signals
(e.g., is enabled) and the bandwidth-select circuit enters the
slow-track mode when a low logic level is inputted (e.g., applied
to the switch).
[0008] The delay circuit comprises delay control logic configured
to operate the APC loop in the fast-track mode before enabling the
laser and operate the APC loop in the slow-track mode when enabling
the laser to operate (e.g., normally, in various code patterns).
The delay control logic enables the APC loop to control power to
the laser before the laser is enabled, thereby providing a stable
laser power output when the laser begins to operate.
[0009] A method of controlling a burst-mode laser may comprise
disconnecting a switch and placing a bandwidth-select circuit in a
fast-track mode when a logic input to an optical network unit (ONU)
in a passive optical network (PON) has a first state, the ONU
including the switch, a laser, a laser driver, a diode and the
bandwidth-select circuit; after the predetermined period of time,
driving the laser using the laser driver and transmitting an
optical signal from the laser normally; when the optical signal
from the laser is stable, placing the bandwidth-select circuit in a
slow-track mode; when the logic input to the ONU has a second
state, turning on the switch to disable the optical signal from the
laser and connect the laser in parallel with the diode; and placing
the bandwidth-select circuit in the fast-track mode when the logic
signal has the first logic state again. In one embodiment, the
first logic state of the logic signal is a high logic level, and
the second logic state of the logic signal is a low logic level.
When the switch is turned on, decreasing a voltage/current at ends
(e.g., the cathode and the anode) of the laser results in no
optical output from the laser.
[0010] Relative to the prior art, the present invention
advantageously provides: [0011] 1. In this invention, a burst-mode
laser driver is replaced by a continuous mode laser driver having a
fast response under the control of a switch and a mode control
circuit. This invention can be used to meet demands of PON systems
for the burst-mode of ONUs, especially for high speed signals, such
as 10G PON applications; and [0012] 2. Low cost and easy
implementation, and adaptability for both DFB laser devices and
EMLs, and ensuring both fast establishment of a stable APC loop and
stable APC loop operation in normal conditions by providing
bandwidth switching using one or more switches and one or more
filter circuits.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a block diagram showing an exemplary circuit
design according to the present invention.
[0014] FIG. 2 is a diagram showing an exemplary EML burst-mode
control circuit according to the present invention.
[0015] FIG. 3 is a diagram showing an exemplary DFB burst-mode
control circuit according to the present invention.
[0016] FIG. 4 is a diagram showing an exemplary bandwidth-select
circuit according to the present invention.
[0017] FIG. 5 is a diagram showing waveforms for sequential logic
to a control the exemplary bandwidth-select circuit, APC loop, and
laser according to the present invention.
DETAILED DESCRIPTION
[0018] Referring to FIG. 1, the present invention provides a
burst-mode laser control circuit. In this invention, an APC loop
including, for example, APC bandwidth select circuit 110,
continuous mode laser driver 120, and laser 130, has an additional
burst-mode control circuit 140, and a switch (FIG. 2) in series
with a diode and in parallel with the laser, which enables the
continuous-mode laser driver 120 to operate in burst-mode by
turning the switch on or off via an external logic signal 160.
Burst-mode control manages the switch and the bandwidth-select
circuit 110 using high or low logic level inputs, wherein the laser
130 is disabled and the bandwidth-select circuit 110 enters a
fast-track mode when the external logic signal 160 has a first
state, such as a high logic level; the laser 130 is enabled and
provides regular optical signals such as burst-mode optical
signals, and the bandwidth-select circuit 110 enters a slow-track
mode, when the external logic signal 160 has a second state, such
as a low logic level. In the slow-track mode, the arrangement
enables the APC loop to operate normally, such as in burst mode
operation.
A First Embodiment
[0019] Referring to FIG. 2, an EML laser device 230 including a
laser 232, a modulator 234 and a monitor photodiode 236, is
controlled at least in part by a burst-mode control circuit
including a switch 240, a diode 242, and a bandwidth tracking
and/or variation control circuit 210. The burst-mode laser control
circuit portion of FIG. 2 provides laser devices with burst-mode
control by turning the switch 240 on or off under the control of an
external logic signal 260, while the switch 240 is in serial
connection with the diode 242 and in parallel connection with the
EML laser device 232. The diode 242 creates a high impedance at the
cathode of the laser 232.
[0020] In addition, the burst-mode control manages the switch 240
and the bandwidth-select circuit 210 in the ONU 200 via a high or
low logic level input 260 from the PON system, wherein, for
example, a TTL (Transistor-Transistor Logic) high logic level may
be between 2.4V and 3.3V, and the low logic level may be between 0V
and 0.8V. The input control logic for the signal 260 is a system
input. The system provides a high or low level input according to
whether the ONU 200 is to be enabled for transmissions.
[0021] The EML 230 is disabled and the bandwidth-select circuit 210
enters the fast-track mode when the burst mode control signal 260
has a first state, such as a high logic level. The EML 230 is
enabled and provides regular optical signals such as burst-mode
optical signals, and the bandwidth-select circuit 210 enters the
slow-track mode, when external logic signal 160 has a second state,
such as a low logic level. In the slow-track mode, the APC loop,
including the bandwidth-select circuit 210, the continuous mode
driver circuitry 220, and the EML 230, ensures a stable optical
power to the EML 230 using the modulation and bias control and
monitoring circuitry 222 in the APC loop.
A Second Embodiment
[0022] FIG. 3 is a circuit diagram 300 of the present invention
employing a DFB laser 330.
[0023] The burst-mode laser control circuit portion including the
switch 340, the diode 342, and the bandwidth tracking and/or
variation control circuit 310 is configured to provide the DFB
laser 330, including laser 332 and monitor photodiode 334, with
burst-mode control by an external logic signal 360 turning the
switch 342 on or off, wherein the switch (e.g., a field effect
transistor) 342 is in serial connection with the diode 344 and in
parallel connection with the DFB laser 332. The diode 342 creates a
high impedance at the cathode of the laser 332.
[0024] Burst-mode control manages the switch 340 and the
bandwidth-select circuit 310 using a high or low logic level input,
wherein the TTL (Transistor-Transistor Logic) high logic level may
be between 2.4V and 3.3V, and the low logic level may be between 0V
and 0.8V. The DFB laser 332 is disabled and the bandwidth-select
circuit 310 enters the fast-track mode when the burst mode control
signal 360 has a first state, such as a high logic level. The DFB
laser 332 is enabled and provides regular and/or burst mode optical
signals, and the bandwidth-select circuit 310 enters the slow-track
mode, when the burst mode control signal 360 has a second state,
such as a low logic level. In the slow-track mode, the APC loop,
including the bandwidth-select circuit 310, laser diode driver
(LDD) 320, and the DFB laser 330, ensures optical power stable to
the DFB laser 330 using the APC loop.
[0025] FIG. 4 is a circuit diagram showing a bandwidth-select
circuit 400 in accordance with embodiments of the present
invention. The bandwidth-select circuit 400 comprises two
functional blocks: a high-low bandwidth selection circuit 410,
comprising a fast-track selection circuit 412 implementing the
fast-track mode, and a slow-track selection circuit 414
implementing the slow-track mode; and a delay circuit 420,
configured to delay the burst-mode control logic input 460 for a
predetermined period of time, such as 20 ns or thereabout, to
operate the APC loop in fast-track mode for the predetermined
period of time (e.g., 20 ns) before the laser is enabled. That is,
during the fast-track mode, automatic power control (APC) can be
quickly established and a stable output power can be provided to
the laser, then in the slow-track mode, the APC loop enables the
laser to operate normally and transmit various code patterns in
burst mode, using a continuous mode laser driver. The input is
generally from a monitor photodiode, and the output is to the laser
driver. The delay circuit 420 may comprise a number of
inverter-type buffers, a simple resistance, a conventional one-shot
pulse generator, etc.
[0026] Resistance R1, resistance R2 and capacitance C1 form
alternative bandwidth selection circuits with different time
constant parameters, wherein R1, switch_band 440 (when closed or
turned on) and C1 form a fast-track circuit which may further
include the parallel resistance R2, and have a first, relatively
low time constant, and when the switch 440 is open or turned off,
R2 and C1 form a slow-track circuit having a second, relatively
high time constant. The greater the time constant .tau.=R*C for the
bandwidth selection circuits, the slower the tracking of automatic
power control adjustment speed is, and vice versa.
[0027] When the switch 440 is turned on, R1 and R2 are in parallel.
For example, if R1 is 10 Ohms, R2 is 200 Ohms, and C1 is 0.01
.mu.F, the RC constant for the fast-track circuit is around
R1*C1=0.1; when the switch 440 is turned off, the RC constant for
the slow-track circuit is about R1*C1=2. Thus, the speed of the
fast-track circuit is about 20 times higher than that of the
slow-track circuit, but the slow-track circuit can average input
signals better to keep the optical output power stable when
burst-mode signals are used to produce optical signals from the
laser.
[0028] FIG. 5 is a diagram showing waveforms of signals in a logic
control sequence chart 500 according to the present invention. When
a control signal 510 from the PON system, the ONU light-emitting
control logic signal, has a high logic level, the switch 240 in
FIG. 2 and/or 340 in FIG. 3 is disconnected. The ONU transmitter
(e.g., the laser) provides optical signals 520, and the laser
driver drives and/or enables the laser normally. However, the
bandwidth-select logic signal 530 remains at a low logic level, for
example for 20 ns, before the optical signal 520 is produced. For
example, the switch control signal (Switch CTR) in FIG. 4 keeps the
switch Switch_band 440 closed while the bandwidth-select circuit
410 is in fast-track mode 540. As the ONU optical signal output 520
becomes stable, the bandwidth-select logic signal 510 remains at
high level, and the switch control signal (Switch CTR) in FIG. 4
keeps the switch 440 open. After the delay for ONU optical signal
creation and/or stabilization, the bandwidth-select circuit 410
transitions the bandwidth select signal 530 to a high logic level,
and the bandwidth-select circuit 410 and the APC loop enter the
slow-track mode, thereby keeping optical signals from the laser
stable.
[0029] When the ONU light-emitting control logic signal 510 has a
low logic level, the switch may be turned on, and the ONU
transmitter disables output of the optical signal 520 from the
laser. The switches 240 in FIGS. 2 and 340 in FIG. 3 are closed,
the laser is connected in parallel with the diode 232 or 332, and
then decreasing the voltage and/or current at ends (e.g., the
cathode and/or anode) of the laser results in no optical output
from the laser. The bandwidth-select circuit remains in fast-track
mode until the ONU control logic signal has a high logic level
again, and the delay of the delay circuit expires.
[0030] In this invention, instead of using burst-mode laser
drivers, continuous-mode laser drivers can operate in burst mode
and have a fast response from the laser, under the external control
of one or more switch circuits. Without requiring burst-mode laser
drivers, this invention can be used to provide PON systems with
burst-mode ONUs, especially for high speed signals, such as 10G PON
applications. This solution has the advantages of low cost, easy
implementation, and easy adaptability for both DFB laser devices
and EMLs. This invention ensures fast creation of stable burst-mode
laser output signals using an APC loop with a continuous-mode laser
driver, and normal burst-mode operations by providing bandwidth
switching in the ACP loop using one or more switches and optional
filter circuits.
* * * * *