U.S. patent application number 11/833047 was filed with the patent office on 2007-11-22 for single fiber passive optical network wavelength division multiplex overlay.
This patent application is currently assigned to Tellabs Bedford, Inc.. Invention is credited to George H. BuAbbud, Michael K. Pratt, Debra Wawro, Muneer Zuhdi.
Application Number | 20070269213 11/833047 |
Document ID | / |
Family ID | 23187393 |
Filed Date | 2007-11-22 |
United States Patent
Application |
20070269213 |
Kind Code |
A1 |
Pratt; Michael K. ; et
al. |
November 22, 2007 |
Single Fiber Passive Optical Network Wavelength Division Multiplex
Overlay
Abstract
A downstream baseline optical signal generated by a baseline
optical link is combined with a second optical signal generated by
an additional optical link to generate a broadband optical signal.
A fiber optic network splits the broadband optical signal to a
plurality of fiber drops. An optical network termination unit
receives the broadband optical signal from the fiber drop and
isolates the downstream baseline optical signal and the second
downstream optical signal from the broadband optical signal. An
upstream baseline optical signal may also be transmitted through
the fiber drop by the optical termination unit. The optical
termination unit does not effect baseline optical service to any
other optical termination unit in the fiber optic network.
Inventors: |
Pratt; Michael K.; (Plano,
TX) ; BuAbbud; George H.; (Southlake, TX) ;
Wawro; Debra; (Arlington, TX) ; Zuhdi; Muneer;
(Lewisville, TX) |
Correspondence
Address: |
BAKER BOTTS L.L.P.
2001 ROSS AVENUE
6TH FLOOR
DALLAS
TX
75201
US
|
Assignee: |
Tellabs Bedford, Inc.
Bedford
TX
|
Family ID: |
23187393 |
Appl. No.: |
11/833047 |
Filed: |
August 2, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10199566 |
Jul 19, 2002 |
7254330 |
|
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11833047 |
Aug 2, 2007 |
|
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60306907 |
Jul 20, 2001 |
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Current U.S.
Class: |
398/66 |
Current CPC
Class: |
H04J 14/0249 20130101;
H04B 10/272 20130101; H04J 14/0226 20130101; H04J 14/0246 20130101;
H04J 14/0252 20130101; H04B 10/27 20130101; H04J 14/0298 20130101;
H04J 14/025 20130101; H04J 14/0247 20130101; H04J 14/0291 20130101;
H04J 14/0245 20130101; H04J 14/0282 20130101; H04J 14/0232
20130101 |
Class at
Publication: |
398/066 |
International
Class: |
H04J 14/00 20060101
H04J014/00 |
Claims
1. An optical network termination unit, comprising: a first filter
operable to receive a broadband optical signal from a fiber drop,
the broadband optical signal including a downstream baseline
optical signal combined with a second downstream optical signal,
the first filter operable to isolate the second downstream optical
signal from the broadband optical signal; a second filter operable
to isolate the downstream baseline optical signal from a remaining
portion of the broadband optical signal after the second downstream
optical signal has been isolated from the broadband optical
signal.
2. The optical network termination unit of claim 1, wherein the
second downstream optical signal is a T-Band signal.
3. The optical network termination unit of claim 2, further
comprising: a wave division multiplexer that separates the T-Band
signal from the broadband optical signal and demultiplexes the
T-Band signal.
4. The optical network termination unit of claim 1, wherein the
second downstream optical signal is an L-Band signal.
5. The optical network termination unit of claim 4, further
comprising: a wave division multiplexer that separates the L-Band
signal from the broadband optical signal and demultiplexes the
L-band signal.
6. The optical network termination unit of claim 1, further
comprising: a converter unit operable to receive an upstream
baseline signal and convert the upstream baseline signal into an
upstream baseline optical signal.
7. The optical network termination unit of claim 6, wherein: the
upstream baseline optical signal is within an optical bandwidth
different from an optical bandwidth of the downstream baseline
optical signal and an optical bandwidth of the second downstream
optical signal; the upstream baseline optical signal, the
downstream baseline optical signal, and the second downstream
optical signal are transmitted through the fiber drop.
8. The optical network termination unit of claim 6, further
comprising: a converter unit operable to receive a second upstream
signal and convert the second upstream signal into a second
upstream optical signal, the second upstream optical signal being
combined with the upstream baseline optical signal for transmission
through the fiber drop.
9. The optical network termination unit of claim 8, wherein the
converter unit generates the second upstream optical signal in a
T-band signal format.
10. The optical network termination unit of claim 8, wherein the
converter unit generates the second upstream optical signal in a
L-band signal format.
11. A method for upgrading a passive optical network, comprising:
receiving a broadband optical signal from a fiber drop, the
broadband optical signal including a downstream baseline optical
signal combined with a second downstream optical signal; isolating
the second downstream optical signal from the broadband optical
signal; isolating the downstream baseline optical signal from a
remaining portion of the broadband optical signal after the second
downstream optical signal has been isolated from the broadband
optical signal.
12. The method of claim 11, further comprising: the second
downstream optical signal is a T-Band signal; separating the T-Band
signal from the broadband optical signal.
13. The method of claim 12, further comprising: demultiplexing the
T-Band signal.
14. The method of claim 11, further comprising: the second
downstream optical signal is an L-Band signal; separating the
L-Band signal from the broadband optical signal.
15. The method of claim 14, further comprising: demultiplexing the
L-Band signal.
16. The method of claim 11, further comprising: passing an upstream
signal through the fiber drop.
17. A system for upgrading a passive optical network, comprising:
means for receiving a broadband optical signal from a fiber drop,
the broadband optical signal including a downstream baseline
optical signal combined with a second downstream optical signal;
means for isolating the second downstream optical signal from the
broadband optical signal; means for isolating the downstream
baseline optical signal from a remaining portion of the broadband
optical signal after the second downstream optical signal has been
isolated from the broadband optical signal.
18. The system of claim 17, further comprising: means for passing
an upstream signal through the fiber drop on a separate bandwidth
from the downstream baseline optical signal and the second
downstream optical signal.
19. The system of claim 17, further comprising: means for
separating a third downstream optical signal from the broadband
optical signal, the third downstream optical signal being a T-band
signal transmitted on a separate bandwidth from the downstream
baseline optical signal and on a separate bandwidth from the second
downstream optical signal.
20. The system of claim 18, further comprising: means for
separating a fourth downstream optical signal from the broadband
optical signal, the fourth downstream optical signal being a L-band
signal transmitted on a separate bandwidth from the downstream
baseline optical signal, the second downstream optical signal, and
the third downstream optical signal.
Description
RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
application Ser. No. 10/199,566 that has issued into U.S. Pat. No.
7,254,330, which claimed priority from and is related to U.S.
Provisional Application No. 60/306,907. These prior applications,
including the entire written description, claims, and drawing
figures, are hereby incorporated into the present application by
reference.
TECHNICAL FIELD
[0002] The present invention relates generally to the field of
broadband multi-media communication systems. More specifically a
single fiber passive optical network wavelength division multiplex
overlay is provided that enables a baseline single fiber passive
optical network to be upgraded on a subscriber by subscriber basis
with a multiplicity of different optical communication links
operating at different optical wavelengths from the baseline
link.
BACKGROUND
[0003] Prior to the explosive growth in the public's demand for
data services, such as dial-up Internet access, the local loop
access network transported mostly voice information. This present
access network typically includes numerous twisted-pair wire
connections between the plurality of user locations and a central
office switch (or terminal). These connections can be multiplexed
in order to more efficiently transport voice calls to and from the
central office. The present access network for the local loop is
designed primarily to carry these voice signals, i.e., it is a
voice-centric network.
[0004] Today, data traffic carried across telephone networks is
growing exponentially, and by many measures may have already
surpassed traditional voice traffic, due in large measure to the
explosive growth of dial-up data connections. The basic problem
with transporting data traffic over this voice-centric network, and
in particular the local loop access part of the network, is that it
is optimized for voice traffic, not data. The voice-centric
structure of the access network limits the ability to receive and
transmit high-speed data signals along with traditional quality
voice signals. Simply put, the access part of the network is not
well matched to the type of information it is now primarily
transporting. As users demand higher and higher data transmission
capabilities, the inefficiencies of the present access network will
cause user demand to shift to other mediums of transport for
fulfillment, such as satellite transmission, cable distribution,
wireless services, etc.
[0005] An alternative present local access network that is
available in some areas is a digital loop carrier ("DLC") system.
DLC systems utilize fiber-optic distribution links and remote
multiplexing devices to deliver voice and data signals to and from
the local users. An early DLC system is described in U.S. Pat. No.
5,046,067 titled "Digital Transmission System" ("the '067 patent").
The '067 patent describes a Digital Loop Carrier (DLC) system. In a
typical DLC system, a fiber optic cable is routed from the central
office terminal (COT) to a host digital terminal (HDT) located
within a particular neighborhood. Telephone lines from subscriber
homes are then routed to circuitry within the HDT, where the
telephone voice signals are converted into digital pulse-code
modulated (PCM) signals, multiplexed together using a time-slot
interchanger (TSI), converted into an equivalent optical signal,
and then routed over the fiber optic cable to the central office.
Likewise, telephony signals from the central office are multiplexed
together, converted into an optical signal for transport over the
fiber to the HDT, converted into corresponding electrical signals
at the HDT, demultiplexed and routed to the appropriate subscriber
telephone line twisted-pair connection.
[0006] Some DLC systems have been expanded to provide so-called
Fiber-to-the-Curb (FTTC) systems. In these systems, the fiber optic
cable is pushed deeper into the access network by routing fiber
from the HDT to a plurality of Optical Network Units (ONUs) that
are typically located within 500 feet of a subscriber's location.
Multi-media voice, data, and even video from the central office
location is transmitted to the HDT. From the HDT, these signals are
transported over the fibers to the ONUs, where complex circuitry
inside the ONUs demultiplexes the data streams and routes the
voice, data and video information to the appropriate
subscriber.
SUMMARY
[0007] A single fiber passive optical network (PON) wavelength
division multiplex (WDM) overlay includes a central office, a fiber
optic network, and a plurality of optical network termination (ONT)
units. The central office has a baseline optical link that receives
a baseline communication signal and converts the baseline
communication signal into a downstream baseline optical signal
within a first optical bandwidth, and has an additional optical
link that receives a second type of communication signal and
converts the second type of communication signal into a second
downstream optical signal within a second optical bandwidth. The
downstream baseline optical signal generated by the baseline
optical link is combined with the second optical signal generated
by the additional optical link to generate a broadband optical
signal. The fiber optic network is coupled to the central office
and receives the broadband optical signal on at least one optic
fiber. The fiber optic network splits the broadband optical signal
to a plurality of fiber drops. The optical network termination
(ONT) units are each coupled to a fiber drop. At least one of the
ONT units is a baseline ONT unit that receives the broadband
optical signal from the fiber drop and splits the downstream
baseline optical signal from the broadband optical signal, and at
least one other of the ONT units is an upgraded ONT unit that
receives the broadband optical signal from the fiber drop and
splits the downstream baseline optical signal and the second
downstream optical signals from the broadband optical signal. In
addition, the installation of the upgraded ONT unit to the PON does
not effect baseline optical service to any other ONT unit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a block diagram of an exemplary single fiber
passive optical network wavelength division multiplex overlay that
includes an enhanced band broadcast sub-carrier modulated (SCM)
signal upgrade;
[0009] FIG. 2 is a graph illustrating exemplary bandwidths for the
communication signals transmitted over the single fiber passive
optical network shown in FIG. 1;
[0010] FIG. 3 is a block diagram of an exemplary single fiber
passive optical network wavelength division multiplex overlay that
includes a course wavelength division multiplexing (CWDM) T-Band
upgrade;
[0011] FIG. 4 is a graph illustrating exemplary bandwidths for the
communication signals transmitted over the single fiber passive
optical network shown in FIG. 3;
[0012] FIG. 5 is a block diagram of an exemplary single fiber
passive optical network wavelength division multiplex overlay that
includes a dense wavelength division multiplexing (DWDM) L-Band
upgrade; and
[0013] FIG. 6 is a graph illustrating exemplary bandwidths for the
communication signals transmitted over the single fiber passive
optical network shown in FIG. 5.
DETAILED DESCRIPTION
[0014] I. Enhanced Band Broadcast Sub-Carrier Modulated (SCM)
Upgrade
[0015] Referring now to the drawing figures, FIG. 1 is a block
diagram of an exemplary single fiber passive optical network
wavelength division multiplex overlay 10 that includes an enhanced
band broadcast sub-carrier modulated (SCM) signal upgrade. The
system 10 includes a plurality of baseline optical network
termination (ONT) units 12, at least one sub-carrier modulated
(SCM) upgraded ONT unit 14, a fiber optic network 18-23, and a
central office 16. The system 10 is preferably a passive optical
network, such as a fiber to the home (FTTH) or fiber to the curb
(FTTC), or fiber to the business (FTTB), that may be upgraded to
include a SCM signal, such as a CATV television signal or a DBS
signal, on a subscriber by subscriber basis without affecting
non-upgraded subscribers.
[0016] Multimedia communication signals, such as
plain-old-telephone signals (POTS), data network signals, CATV
signals and DBS signals, are received from various service
providers at the central office (CO) 16. The central office (CO) 16
converts the multimedia signals into optical signals at different
wavelengths and multiplexes the various optical multimedia signals
onto single fibers in the fiber optic network 18-23. The fiber
optic network 18-23 distributes the optical signals to optical
network termination (ONT) units 12, 14, which filter or demultiplex
the optical signals into their individual multimedia components,
and convert the filtered optical signals into electrical signals
for use in the home or office. An upgraded SCM ONT unit 14 may
filter a received optical signal into its baseline (telephony/data)
and SCM components, and a non-upgraded baseline ONT unit 12 may
filter a received optical signal into a baseline signal without
being affected by the SCM component of the received signal. In
addition, in a bidirectional system, both the non-upgraded baseband
ONT units 12 and the upgraded SCM ONT units 14 may convert baseline
transmissions from the home (i.e., upstream telephony/data signals)
into optical signals at a different optical wavelength than the
incoming (i.e., downstream) signals and transmit the signals over
the fiber optic network 18-23 to the CO 16. [0017] A. Fiber Optic
Network
[0018] The fiber optic network 18-23 shown in FIG. 1 is a
point-to-multipoint single fiber network that includes an outside
plant 20, 21, a plurality of passive remote splitters 23, and a
plurality of distribution splitters 18. The outside plant 20, 21
includes individual optic fibers or bundles of individual optical
fibers with each individual fiber coupled between a route
protection switch 46 in the central office 16 and a passive remote
splitter 23. The illustrated embodiment includes two optic paths, a
main path 20 and a redundant path 21, between the central office 16
and the passive remote splitters 23. Each route protection switch
46 in the central office 16 is, therefore, coupled to one passive
remote splitter 23 via two individual optic fibers--one main fiber
and one redundant fiber.
[0019] Each individual fiber and its redundant pair in the
illustrated outside plant 20, 21 may provide service to thirty-two
(32) homes. The passive remote splitters 23 are eight-to-two (8:2)
splitters that divide the main and redundant fibers 20, 21 into
eight distribution fibers. The optical signals are transmitted for
short distances over the distribution fibers, without
amplification, before termination at a four-to-one (4:1)
distribution splitter 18 located in close proximity to four ONT
units. A distribution splitter 18 terminates a distribution fiber
to four single drop fibers 19 that extend from the distribution
splitter 18 to a home or office and terminate at an ONT unit 12,
14. The distribution splitters 18, the fiber drops 19, and the ONT
units 12, 14 are added to the system 10 as service is required.
[0020] B. Central Office
[0021] The central office 16 shown in FIG. 1 includes a passive
cross-connection unit 22, an optical video distribution sub-system
25, two baseline optical line termination (OLT) units 24, and a
route protection control circuit 52. In operation, the central
office 16 interfaces the fiber optic network 18-23 with
communication service providers, such as CATV, DBS, and
telephony/data services.
[0022] The baseline OLT units 24 each include a baseline
splitting-blocking filter combination 56, a downstream (DS)
optical-electrical converter (OEC) 58, and an upstream
optical-electrical converter 60. The downstream OEC 58 receives
telephony/data signals from POT and data network service providers,
for example over a public telephone network, and converts the
telephony/data signals into optical signals at a selected optical
bandwidth for transmission to the ONT units 12, 14. Each baseline
OLT unit 24 may provide optical telephony/data signals, without
amplification, to a set number of ONT units 12, 14. For example, in
the illustrated embodiment, each baseline OLT unit 24 can supply
thirty-two (32) ONT units 12, 14. If more than thirty-two (32) ONT
units 12, 14 require baseline service, then additional baseline OLT
units 24 must be added at the CO 16. The illustrated CO 16 includes
two baseline OLT units 24, and can thus supply sixty-four (64) ONT
units 12, 14, without amplification.
[0023] The baseline splitting-blocking filter combination 56 in an
OLT unit 24 receives an optical downstream signal from the
downstream OEC 58 and also receives an upstream signal from the
fiber optic network 18-23 via a fiber connection 62 with the
passive cross-connection unit 22. The baseline splitting-blocking
filter combination 56 passes the downstream telephony/data signals
to the fiber connection 62 with the passive cross-connection unit
22, and splits the upstream (US) telephony/data signal received
from the passive cross-connection unit 22. The isolated upstream
(US) telephony/data signals are converted into electrical signals
by the upstream OEC 60, and are transmitted to the service
provider. In a bi-directional system, the upstream (US)
telephony/data signals are transmitted at a different bandwidth and
on the same optic fiber as the downstream (DS) telephony/data
signals. Exemplary optical bandwidths for the upstream and
downstream telephony/data signals are described below with
reference to FIG. 2.
[0024] The optical video distribution sub-system 25 includes an SCM
module 26, a high power optical amplifier 28, and an optical
splitter 30. The SCM module 26 receives video signals, such as CATV
or DBS signals, that enter the CO 16 from the service provider
head-end and/or satellite. The SCM module 26 combines the video
signals from the service providers into one optical signal at a
selected bandwidth. An exemplary optical bandwidth for the SCM
signal is described below with reference to FIG. 2. The optical SCM
signal from the SCM module 26 is then amplified by the high power
optical amplifier 28, and split into a plurality of optical SCM
transmission signals by the optical splitter 30.
[0025] The passive cross-connection unit 22 includes a plurality of
wave division multiplexers (WDMs) 54 and a plurality of optical
route protection switches 46. The WDMs 54 each include two
inputs--one input coupled to an optical SCM signal generated by the
optical video distribution sub-system 25, and one input coupled to
the optical output 62 from a baseline OLT unit 24. The WDMs 54
combine the downstream telephony/data signal from the baseline OLT
unit 24 and the SCM signal from the optical video distribution
sub-system 24 into one broadband optical signal.
[0026] The broadband optical signals generated by the WDMs 54 are
coupled to the fiber optic network 18-23 through the optical route
protection switches 46. Each optical route protection switch 46
includes an input that receives a broadband optical signal from a
WDM 54, a control input from the route protection control circuit
52, and two optical fiber outputs 48, 50. The two optical fiber
outputs 48, 50 from an optical route protection switch 46 are
coupled to a passive remote splitter 23 through separate paths in
the outside plant 20, 21. The route protection control circuit 52
monitors the optical continuity of the outside plant 20, 21, and
routes the broadband optical signal through either the main or
redundant path 20, 21 to adjust for any discontinuity. For example,
the optical route protection switches 46 may be configured to
connect the broadband optical signals to the main path 48, 20
during normal operation. If the route protection control circuit 52
detects a discontinuity in the main path 20, then the route
protection control circuit 52 may cause one or more of the optical
route protection switches 46 to switch the broadband optical
signals from one or more individual optic fibers in the main path
20 to the corresponding redundant fibers in the redundant path 50,
23 in order to prevent interruptions in service. [0027] C. Optical
Network Termination (ONT) Units
[0028] Two types of optical network termination (ONT) units are
illustrated in FIG. 1: a SCM upgraded ONT unit 14, and a
non-upgraded baseline ONT unit 12. Both the SCM upgraded ONT units
14 and the non-upgraded baseline ONT units 12 may be used to
transmit and receive baseline telephony/data signals via the fiber
optic network 18-23. The SCM upgraded ONT units 12, however, may
also receive broadcast video signals, such as CATV or DBS signals,
over the same optic fiber without affecting baseline service to the
non-upgraded ONT units 12.
[0029] A baseline ONT unit 12 includes a baseline
splitting-blocking filter combination 32, a downstream (DS)
optical-electrical converter (OEC) 36, and an upstream
optical-electrical converter (OEC) 34. The baseline
splitting-blocking filter combination 32 receives a broadband
optical signal 32 from a fiber drop 19 and filters the signal 32 to
isolate downstream (DS) telephony/data signals 35, which fall
within a designated optical bandwidth. The downstream (DS)
telephony/data signals are coupled to the downstream (DS)
optical-electrical converter (OEC) 36, which converts the optical
telephony/data signals into electrical signals for use by equipment
within the home or office. In addition, the baseline
splitting-blocking filter combination 32 also receives upstream
(US) telephony/data signals 33 and passes the upstream (US) signals
to the fiber drop 19 for transmission to the central office 16 via
the fiber optic network 18-23. The upstream (US) telephony/data
signals are generated by equipment within the home or office, and
converted to optical signals by the upstream (US) OEC 34. As noted
above, the upstream (US) telephony/data signals in a bi-directional
system are transmitted at a different bandwidth and on the same
optic fiber as the downstream (DS) telephony/data signals.
[0030] An upgraded SCM ONT unit 14 is similar to the baseline ONT
unit 12, with the inclusion of a SCM splitting-blocking filter
combination 40 and a SCM optical-electrical converter (OEC) 42. The
broadband optical signal 38 from the fiber drop 19 is received by
the SCM splitting-blocking filter combination 40 which filters the
broadband signal 38 to isolate optical SCM signals 41 and to pass
baseline telephony/data signals 44. The isolated SCM signals 41 are
coupled to the SCM OEC 42, and the isolated baseline telephony/data
signals 44 are coupled to the baseline splitting-blocking filter
combination 32. The SCM optical-electrical converter 42 converts
the optical SCM signals 41 into electrical signals for use by video
equipment within the home or office. The baseline
splitting-blocking filter combination 32 filters the baseline
telephony/data signals 44 to isolate downstream (DS) telephony/data
signal 35 which are converted to electrical signals by the
downstream (DS) OEC 36. In addition, both the baseline
splitting-blocking filter combination 32 and the SCM
splitting-blocking filter combination 40 pass upstream (US)
telephony/data signals 33 for transmission to the central office 16
via the optical network 18-23. [0031] D. Optical Bandwidths
[0032] FIG. 2 is a graph illustrating exemplary bandwidths for the
communication signals transmitted over the single fiber passive
optical network 10 shown in FIG. 1. As illustrated, an upstream
(US) telephony/data signal 102, a downstream (DS) telephony/data
signal 104 and a SCM signal 106 are each transmitted at different
wavelengths over the same optic fiber. The upstream (US)
telephony/data signal 102 may have a bandwidth of about 1260-1360
nm, the downstream (DS) telephony/data signal 104 may have a
bandwidth of about 1480-1500 nm, and the SCM signal 106 may have a
bandwidth of about 1535-1565 nm. Also illustrated in FIG. 2 are the
filter characteristics of the baseline and SCM splitting-blocking
filters 32, 40, 56 in the ONTs 12, 14 and at the central office 16.
The baseline splitting-blocking filters 32, 56 include a band-pass
filtering characteristic (between about 1460 and 1525 nm) that
isolates or passes downstream (DS) signals, and a low-lass
filtering characteristic (below about 1430 nm) that isolates or
passes upstream (US) signals. The SCM splitting-blocking filter 40
includes a band-pass filtering characteristic (between about 1510
and 1580 nm) that isolates SCM signals.
[0033] As noted above, the passive optical network 10 may be a
bi-directional system in which both upstream and downstream signals
are transmitted, at different wavelengths, on the same optic fiber.
The downstream (DS) telephony/data signals 104 and the SCM signals
106 are multiplexed into broadband signals that are transmitted
from the central office 16 to both the non-upgraded baseline ONT
units 12 and the upgraded SCM ONT units 14. The direction of the
multiplexed SCM and DS signals 104, 106 in the bi-directional
system 10 is illustrated in FIG. 2 by the downward pointing arrows.
The upstream (US) telephony/data signals 102 are transmitted from
the ONT units 12, 14 to the central office 16 over the same optic
fibers as the multiplexed DS and SCM signals 104, 106. The
direction of the US signals 102 in the bidirectional system 10 is
illustrated in FIG. 2 by the upward pointing arrow.
[0034] II. Course Wavelength Division Multiplexing (CWDM) T-Band
Upgrade
[0035] FIG. 3 is a block diagram of an exemplary single fiber
passive optical network (PON) wavelength division multiplex overlay
200 that includes a course wavelength division multiplexing (CWDM)
T-Band upgrade. This CWDM T-Band upgraded PON 200 is similar to the
SCM upgraded PON 10 described above with reference to FIGS. 1 and
2, except the CWDM T-Band upgrade 200 also enables T-Band CWDM
signals to be transmitted on the same optic fibers as the baseline
and SCM signals without affecting subscribers that have not
upgraded to a T-Band upgraded optical network termination (ONT)
unit 202. The CWDM T-Band upgrade may, for example, be added to a
baseline system or the SCM upgraded PON 10 described above without
any substantial effect to the existing services. [0036] A. Central
Office
[0037] The central office 16 in the CWDM T-Band upgraded PON 200
includes the passive cross-connection unit 22, optical video
distribution sub-system 25, and baseline optical line termination
(OLT) units 24, as described above with reference to FIG. 1. In
addition, the central office 16 is upgraded to include a CWDM
optical line termination (OLT) unit 210 and an additional WDM
multiplexer 214. It should be understood, however, that in other
embodiments the CWDM upgrade may be added to a baseline PON that
does not include an SCM upgrade.
[0038] The CWDM OLT unit 210 in the CO 16 receives multimedia
transmissions from a service provider and multiplexes the
multimedia signals into an optical downstream T-Band signal 208. A
T-Band signal may, for example, be used to provide an upgraded CWDM
ONT unit 202 with a higher data rate link than that available from
a baseline service, or for other high bandwidth applications. In
addition, several different multimedia signals may be
simultaneously transmitted at different wavelengths within the
multiplexed CWDM T-Band signal 208. For instance, a CWDM service
provider may offer one type of service, such as a video or data
service, carried over one wavelength in the T-Band signal, and
another type of service, such as voice, simultaneously carried over
another wavelength.
[0039] The downstream T-Band signal 208 generated by the CWDM OLT
210 is combined with a downstream (DS) baseline signal by the WDM
multiplexer 214 to generate a multiplexed CWDM/baseline output
signal 216. The output signal 216 from the WDM multiplexer 214 is
then coupled as one of the inputs to a WDM multiplexer 54 in the
cross-connection unit 22, which combines the multiplexed
CWDM/baseline signal 216 with a SCM signal from the optical video
distribution sub-system 25 to generate the broadband signal
transmitted over the optical network 12-23. With respect to
incoming signals from the ONTs 12, 14, 202, the additional WDM
multiplexer 214 also operates as a demultiplexer to separate
upstream T-Band signals generated at a T-Band upgraded ONT unit 202
from upstream (US) baseline signals. The isolated upstream (US)
baseline signals are coupled to the baseline OLT 24 and transmitted
to the baseline service provider as described above. The isolated
upstream CWDM T-Band signals are coupled to the CWDM OLT 210, which
separates the T-Band signal into its multimedia components, and
transmits the signals to the service provider. [0040] B. T-Band
Upgraded ONT Unit
[0041] The T-Band upgraded ONT unit 202 includes a CWDM ONT unit
204, a WDM multiplexer (W1) 206, and either a baseline ONT unit 12
or a SCM upgraded ONT unit 14. In operation, the T-Band upgraded
ONT unit 202 may send and receive T-Band signals 208 over the fiber
optic network 18-23 using the CWDM ONT unit 204, and, depending on
the additional services purchased, may also receive baseline
telephony/data service and video service with an integral baseline
or SCM upgraded ONT unit 12, 14.
[0042] The WDM multiplexer (W1) 206 in the T-Band upgraded ONT unit
202 is coupled to a fiber drop 19 in the fiber optic network 18-23,
and receives incoming broadband optical signals that may include
downstream baseline, SCM, and downstream T-Band signal components.
With respect to the incoming signals, W1 206 operates as a
demultiplexer to separate the downstream T-Band signal components
from the downstream baseline and SCM signal components. The
downstream T-Band signals are coupled to the CWDM ONT unit 202, and
the downstream baseline and SCM signals are coupled to the integral
baseline or SCM upgraded ONT unit 12, 14. The CWDM ONT unit 202
splits the downstream T-Band signal 208, and demultiplexes the CWDM
T-Band signal 208 into its multimedia components. In addition,
upstream CWDM T-Band signals 208 generated by the CWDM ONT unit 202
are combined with upstream (US) baseline signals by the WDM
multiplexer (W1) 206, and are transmitted to the CO 16 via the
fiber optic network 18-23. [0043] C. Optical Bandwidths
[0044] FIG. 4 is a graph 300 illustrating exemplary bandwidths for
the communication signals transmitted over the single fiber passive
optical network 200 shown in FIG. 3. As illustrated, an upstream
(US) telephony/data signal 102, a downstream (DS) telephony/data
signal 104, a SCM signal 106, a downstream T-Band signal 302, and
an upstream T-Band signal 304 are each transmitted at different
wavelengths over the same optic fiber. As noted above, the upstream
(US) telephony/data signal 102 may have a bandwidth of about
1260-1360 nm, the downstream (DS) telephony/data signal 104 may
have a bandwidth of about 1480-1500 nm, and the SCM signal 106 may
have a bandwidth of about 1535-1565 nm. In addition, the downstream
and upstream T-Band signals 302, 304 may fill the available
bandwidth (1360-1480 nm) between the US and DS baseline signals
120, 104. The downstream T-Band signals 302 may have a bandwidth of
about 1360-1430 nm, and the upstream T-Band signal 304 may have a
bandwidth of about 1430-1480 nm.
[0045] Also illustrated in FIG. 4 are the filter characteristics of
the baseline and SCM splitting-blocking filters 32, 40, 56 in the
ONTs 12, 14 and at the central office 16, as described above. In
addition, the direction (i.e., upstream or downstream) of the
signals is illustrated in FIG. 4 by the direction of the arrows
above the bandwidth for the particular signal type. Upward-facing
arrows represent upstream signals, and downward-facing arrows
represent downstream signals.
[0046] III. Dense Wavelength Division Multiplexing (DWDM) L-Band
Upgrade
[0047] FIG. 5 is a block diagram of an exemplary single fiber
passive optical network wavelength division multiplex overlay 400
that includes a dense wavelength division multiplexing (DWDM)
L-Band upgrade. This DWDM L-Band upgraded PON 400 is similar to the
CWDM T-Band upgraded PON 200 described above with reference to FIG.
3, except the DWDM L-Band upgrade 400 also enables L-Band DWDM
signals to be transmitted on the same optic fibers as the baseline,
SCM, and T-Band signals without affecting subscribers that have not
upgraded to an L-Band upgraded ONT unit 402. [0048] A. Central
Office
[0049] The central office (CO) 16 in the DWDM L-Band upgraded PON
400 includes optical video distribution sub-system 24, baseline OLT
units 24, and CWDM OLT unit 210, as described above with reference
to FIG. 3. In addition, the CO 16 is upgraded to include a DWDM OLT
unit 410, and the cross-connection unit 22 is upgraded to include
an additional WDM multiplexer (W2) 414. It should be understood,
however, that in other embodiments the DWDM L-Band upgrade could be
added to a baseline PON that does not include a SCM or CWDM
upgrade.
[0050] The DWDM OLT unit 410 in the CO 16 receives multimedia
transmissions from a service provider and multiplexes the
multimedia signals into an optical downstream L-Band signal 408.
The DWDM multiplexing scheme employed by the DWDM OLT unit 410 is
similar to the CWDM multiplexing scheme of the CWDM OLT unit 210,
as described above. An L-Band DWDM multiplexer, however, combines
multiple signals at a higher frequency and less sensitive bandwidth
than a T-Band CWDM multiplexer, and can, therefore, combine more
signals into a lesser amount of bandwidth. Other advantages of
L-Band transmission over T-Band transmission are generally known to
those skilled in the art of passive optical networks.
[0051] The downstream L-Band signal 408 generated by the DWDM OLT
410 is coupled to an input of the additional WDM multiplexer (W2)
414 in the cross-connection unit 22, which combines the L-Band
signal 408 with a broadband signal generated by one of the other
WDM multiplexers 54 in the cross-connection unit 22. With respect
to incoming signals from the ONTs 12, 14, 202, 402, the additional
WMD multiplexer (W2) 414 in the cross-connection unit 22 operates
as a demultiplexer to separate upstream L-Band signals 408
generated as an L-Band upgraded ONT unit 402 from other upstream
signals. The isolated upstream L-Band signals 408 are coupled to
the DWDM OLT 410, which separates the L-Band signal into its
multimedia components, and transmits the signals to a service
provider. [0052] B. L-Band Upgraded ONT unit
[0053] The L-Band upgraded ONT unit 402 includes a DWDM ONT unit
404, a WDM multiplexer (W2) 406, and either a baseline ONT unit 12
or a SCM upgraded ONT unit 14. In operation, the L-Band upgraded
ONT unit 402 may send and receive L-Band signals 408 over the fiber
optic network 18-23 using the DWDM ONT unit 404, and, depending on
the additional services purchased, may also receive baseline
telephony/data service and video service with an integral baseline
or SCM upgraded ONT unit 12, 14.
[0054] The WDM multiplexer (W2) 406 in the L-Band upgraded ONT unit
402 is coupled to a fiber drop 19 in the fiber optic network 18-23,
and receives incoming broadband optical signals that may include
downstream baseline, SCM, downstream T-Band, and downstream L-Band
components. With respect to the incoming signals, W2 406 operates
as a demultiplexer to separate the downstream L-Band signal
components from other components of the incoming broadband signal.
The downstream L-Band signals 408 are coupled to the DWDM ONT unit
404, and the other signal components are coupled to the integral
baseline or SCM upgraded ONT unit 12, 14. The DWDM ONT unit 404
splits the downstream L-Band signal 408, and demultiplexes the
L-Band signal 408 into its multimedia components. In addition,
upstream DWDM L-Band signals 408 generated by the DWDM ONT unit 404
are combined with upstream (US) baseline signals by the WDM
multiplexer (W2) 406, and are transmitted to the CO 16 via the
fiber optic network 18-23. [0055] C. Optical Bandwidths
[0056] FIG. 6 is a graph 500 illustrating exemplary bandwidths for
the communication signals transmitted over the single fiber passive
optical network 400 shown in FIG. 5. As illustrated, an upstream
DWDM L-Band signal 502 and a downstream DWDM L-Band signal 504 are
transmitted over a single optic fiber and at different wavelengths
than baseline, SCM, and CWDM T-Band signals. As noted above, the
upstream (US) telephony/data signal 102 may have a bandwidth of
about 1260-1360 nm, the downstream (DS) telephony/data signal 104
may have a bandwidth of about 1480-1500 nm, the SCM signal 106 may
have a bandwidth of about 15351565 nm, the downstream T-Band
signals 302 may have a bandwidth of about 1360-1430 nm, and the
upstream T-Band signal 304 may have a bandwidth of about 1430-1480
nm. In addition, the DWDM L-Band signals 502, 504 may fill the
available high-frequency bandwidth (15601600 nm) above the SCM
signal 106. The upstream L-Band signal 502 may have a bandwidth of
about 1560-1580 nm, and the downstream L-Band signal 504 may have a
bandwidth of about 1580-1600 nm.
[0057] Also illustrated in FIG. 5 are the filter characteristics of
the baseline and SCM splitting-blocking filters 32, 40, 56 in the
ONTs 12, 14 and at the central office 16, as described above. In
addition, the direction (i.e., upstream or downstream) of the
various signals is illustrated in FIG. 5 by the direction of the
arrows above the bandwidth for the particular signal type.
Upward-facing arrows represent upstream signals, and
downward-facing arrows represent downstream signals.
[0058] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to make and use the invention. The patentable
scope of the invention is defined by the claims, and may include
other examples that occur to those skilled in the art.
* * * * *