WO2001097426A2 - Apparatus and method for demultiplexing a time multiplexed signal - Google Patents
Apparatus and method for demultiplexing a time multiplexed signal Download PDFInfo
- Publication number
- WO2001097426A2 WO2001097426A2 PCT/US2001/040968 US0140968W WO0197426A2 WO 2001097426 A2 WO2001097426 A2 WO 2001097426A2 US 0140968 W US0140968 W US 0140968W WO 0197426 A2 WO0197426 A2 WO 0197426A2
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- WO
- WIPO (PCT)
- Prior art keywords
- signal
- modulator
- signals
- modulators
- demultiplexed
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/06—Polarisation multiplex systems
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/08—Time-division multiplex systems
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/08—Time-division multiplex systems
- H04J14/083—Add and drop multiplexing
Definitions
- time-division multiplexing has been used to combine multiple data streams at relatively slow data rates into a combined stream at a faster overall composite rate.
- TDM processing at the transmitting side, individual bits (or packets of bits) of the component data stream signals are interleaved in time, such as by alternating bit time windows.
- the individual component signals can be recovered.
- two individual lOGb/s signals can be combined into a single 20Gb/s signal by interleaving the bits of the two signals.
- the receiver can extract alternating bits from the received composite signal to recover the two component signals.
- the present invention is directed to an apparatus and method for improved demultiplexing of a time-multiplexed signal which permits very high data rates.
- the demultiplexing system of the invention includes an input interface over which a multiplexed signal, such as, for example, a TDM signal, can be received.
- the multiplexed signal is a combination of a plurality of component signals, each of which is modulated at a unique one of a plurality of modulation frequencies.
- at least one modulator receives the multiplexed signal from the input interface and at least partially demultiplexes the signal into a pair of at least partially demultiplexed signals.
- the at least partially demultiplexed signals are routed toward a plurality of receivers.
- At least one receiver is adapted to detect signals at an associated respective one of said modulation frequencies.
- Each receiver provides a feedback signal indicative of an intensity of a received signal at its associated modulation frequency.
- the feedback signal is used to adjust a parameter of the modulator such that the component signal modulated at the associated modulation frequency can be recovered from the signal received by the receiver.
- the modulation signal applied to each component signal is a very low frequency signal relative to the data rate of the component signal.
- the modulation frequency of one of the component signals is on the order of 10 "7 times the data rate of the component signal.
- the data rate of each component signal can be 10 Gbits/sec.
- the modulation frequency can be in the kilohertz range.
- the modulation frequencies for each of four lOGbits/sec component signals are 1.0 kHz, 1J kHz, 1.2 kHz and 1.3 kHz.
- the modulation depth is below 100 percent.
- the modulation depth is below 10 percent and can be, for example 1 percent or 2 percent.
- the modulator is an electro-optical modulator and, in one particular embodiment, is a Y-fed balanced bridge intensity modulator.
- the modulator includes a bias input which adjusts the modulator output based on the applied bias voltage.
- the feedback signal from the receiver can be used to adjust the bias port of the modulator and/or the RF phase at an RF input port of the modulator.
- the demultiplexer of the invention can include multiple modulators configured to demultiplex the multiplexed signal in multiple stages.
- the signal is demultiplexed in two stages.
- a first stage includes a single modulator which receives the multiplexed signal and at least partially demultiplexes the signal into a pair of partially demultiplexed signals to partially demultiplex the signal.
- the first stage modulator can demultiplex the multiplexed signal into two 20 Gb/s signals.
- the partially demultiplexed signals are routed from the outputs of the first-stage modulator to a respective pair of second-stage modulators.
- Each of the second-stage modulators further demultiplexes its input signal into another pair of further demultiplexed signals.
- each second-stage modulator demultiplexes its 20Gb/s input signal into a pair of 10 Gb/s demultiplexed signals.
- the multiplexed signal is formed by applying a different modulation at a unique modulation frequency to each of a group of component signals and then combining the modulated component signals.
- the modulation applied to each component signal serves to uniquely identify the component signal.
- the demultiplexer includes multiple receivers, each of which is tuned to one of the modulation frequencies used to create the multiplexed signal. Feedback from one or more of the tuned receivers is used to set up the modulators to route the component signals to the appropriate receivers as they are recovered from the multiplexed signal by the modulators.
- the system is set up or turned on in a very efficient fashion. First, a first turn-on or set-up signal is activated at one of the modulation frequencies.
- the signal is applied to the first-stage modulator which splits the signal and routes the split signals to the second-stage modulators which split the signals again.
- the second-stage modulators route the further split signals toward the receivers.
- the receiver that is tuned to the selected modulation frequency of the first turn-on signal provides a feedback signal which is used to adjust the first- stage and second-stage modulators associated with the receiver.
- the bias input signals and/or the RF phase at the RF inputs of the modulators are adjusted to maximize the intensity of the signal received by the receiver tuned to the turn-on signal modulation frequency. When this condition is achieved, the receiver is
- Both the associated first-stage and second-stage modulators route all of the energy at the modulation frequency out of a first output and route other signals out of the second output. This process is then repeated for another of the receivers.
- a second turn-on signal at another of the modulation frequencies is applied to the first-stage modulator.
- the signal at the second modulation frequency is routed out of the second output of the first-stage modulator toward the second-stage modulator, which splits the signal and routes the split signals toward the final two receivers.
- the one of the receivers that is tuned to the turn-on signal modulation frequency provides the feedback signal used to adjust the bias input and the RF phase input of the associated second-stage modulator.
- the bias input and RF phase of the RF input are adjusted by the feedback signal to maximize the intensity of the signal at the second modulation frequency at the associated second receiver.
- the second receiver is "locked" to the second modulation frequency.
- FIG. 1 contains a schematic block diagram of one embodiment of a demultiplexing system in accordance with the present invention.
- FIG. 2 contains a schematic diagram illustrating one type of signal time multiplexing to which the present invention is applicable.
- FIG. 3 contains a schematic flowchart which illustrates the logical flow of a turn-on procedure for the system of the invention in accordance with the invention.
- FIG. 1 is a schematic block diagram of one embodiment of a demultiplexing system 10 in accordance with the present invention.
- a time-multiplexed signal is received at an input interface 8.
- FIG. 2 is a schematic diagram which generally illustrates one form of time multiplexing which can be used to generate the time- multiplexed signal to which the invention is applicable.
- a technique for multiplexing N channels or signals is illustrated. Multiplexing of the N bit streams is achieved by a delay technique.
- the laser 2 generates a periodic pulse train at the repetition rate equal to the single-channel bit rate B.
- the pulse train output is split into N branches, after amplification if necessary, and a modulator 5(1), 5(2), ..., 5(N) in each branch blocks the pulse for every 0 bit, creating N independent bit streams at the bit rate B.
- Each of the individual signals in each branch is modulated at a different identifying modulation frequency by modulators 5(1), 5(2), ..., 5(N).
- Multiplexing of N bit streams is achieved by individually set delays 4(1), 4(2), ..., 4(N) in each branch.
- the outputs of all the branches are combined to form a composite signal.
- the composite signal bit rate is 40 Gb/s.
- the time-multiplexed signal to which the present invention is applicable can be generated by a transmission and multiplexing system such as the one described in copending U. S. Patent Application serial number 09/566,303, filed on May 8, 2000, entitled, "Bit Interleaved Optical Multiplexer," of the same assignee as the assignee of the present application.
- a transmission and multiplexing system such as the one described in copending U. S. Patent Application serial number 09/566,303, filed on May 8, 2000, entitled, "Bit Interleaved Optical Multiplexer," of the same assignee as the assignee of the present application.
- the contents of that application are incorporated herein in their entirety by reference.
- the multiplexed signal is routed from the input 8 to the input of a first electro-optical modulator 12.
- First and second outputs of the first modulator 12 are routed on lines 13 and 15, respectively, as shown to the inputs of a second modulator 14 and a third modulator 16, respectively.
- each of the modulators is a Y-fed balanced bridge modulator, or the like, such as those manufactured and sold by JDS Uniphase Corporation.
- the first modulator 12 receives the multiplexed signal from the input 8 and partially demultipexes the signal into two partially demultiplexed signals.
- the first output signal from the modulator 12 is provided on line 13 as the input to a second modulator 14.
- the second output of the modulator 12 is provided on line 15 to the input of the third modulator 16.
- the modulator 14 further dmultipexes its received signal into two demultiplexed signals and routes its first and second demultiplexed outputs on lines 54 and 56 to receivers 18 and 20, respectively.
- the modulator 16 further demultiplexes its input signal into two demultiplexed signals and routes its first and second demultiplexed output signals on lines 58 and 60 to the receivers 22 and 24, respectively.
- each component signal in the multiplexed signal is characterized by a unique modulation frequency which serves to identify and distinguish the component signal from the other component signals. This unique modulation is used by the system 10 to recover the component signals.
- each receiver 18, 20, 22 and 24 is tuned to a particular modulation frequency.
- the modulations will be referred to herein as A, B, C and D.
- receiver 18 is tuned to detect signals with modulation A
- receiver 20 is tuned to detect signals with modulation B
- receiver 22 is tuned to detect signals with modulation C
- receiver 24 is tuned to detect signals with modulation D.
- the modulation signal applied to each component signal is a very low frequency signal relative to the data rate of the component signal.
- the modulation frequency of one of the component signals is on the order of 10 "7 times the data rate of the component signal.
- the data rate of each component signal can be 10 Gbits/sec.
- each of the receivers 18, 20, 22 and 24 includes detection circuitry used to detect its respective associated subcarrier modulation to recover the data at its incoming component data rate, e.g., lOGb/s. The data is recovered from the signal, and a clock signal at the data rate is generated from the incoming data. As shown in FIG.
- receiver 18 generates a clock signal from the recovered data stream, and feeds back the clock signal to a pair of phase shifters 30 and 32 on lines 42 and 44, respectively.
- a processor 26 uses a signal indicative of the intensity of the modulation A signal recieved at the receiver 18 to generate a phase control signal used to control the amount of phase shift in phase shifter 30 and provides the control signal to phase shifter 30 on line 48.
- the processor 26 also generates another phase control signal used to control the amount of phase shift in phase shifter 32 and provides the control signal to phase shifter 32 on line 52.
- phase shifted signals are applied to the RF inputs of the modulators 12 and 14 to precisely control the delay of the signals through the modulators such that the component signals can be accurately recovered from the multiplexed composite signal.
- the frequency of the signal fed back to modulator 12. is doubled by frequency doubler 34 because the modulator 12 operates to generate the partially demultiplexed signals on lines 13 and 15 at twice the frequency at which the modulator 14 operates.
- Receiver 24 also generates a feedback clock signal and provides the feedback signal to phase shifter 36.
- the processor 28 generates another phase control signal and applies the control signal via line 50 to phase shifter 36 to control the phase shift introduced into the feedback clock signal. Once again, this is done to control the timing of the demultiplexing process of the invention.
- Receiver 18 also provides a feedback signal on line 38 which is indicative of the intensity of received signal having modulation A.
- the feedback signal is routed to the processor 26 which uses the feedback signal to generate the control signals used to adjust the bias input and the RF phase at the RF input of the modulator 14.
- the bias input control signal is routed to the bias input of the modulator 14 on line 49.
- the RF phase control signal is routed to the phase shifter 30 on line 48.
- the lOGb/sec clock signal recovered by the receiver 18 is routed on line 42 to the phase shifter 30.
- the control signal from the processor 26 on line 48 controls the phase shift of the clock signal introduced by the phase shifter 30.
- the phase shifted clock signal is applied to the RF input of the modulator 14.
- the bias input and RF inputs are adjusted to maximize the intensity of the modulation A signal at the receiver 18.
- all signal with modulation A received by the modulator 14 is routed via the first output of the modulator 14 on line 54 to receiver 18.
- the remaining signal is routed via the second Output of modulator 14 on line 56 to receiver 20.
- the processor 26 also generates control signals used to control the bias input and the RF input to the first modulator 12.
- the second bias control signal is applied to the bias input of modulator 12 via line 55, and the second phase control signal is applied to the phase shifter 32 via line 52.
- the phase shifter 32 adjusts the phase of the 10 Gb/sec clock signal recovered by the receiver 18 and applies the phase shifted clock signal through the frequency doubler 34 to the RF input of the modulator 12.
- modulator 12 routes signals with modulation A and B via its first output on line 13 to modulator 14.
- the remaining signals, i.e., signals with modulations C and D, are routed via the second output of modulator 12 on line 15 to the third modulator 16.
- Modulator 16 further demultiplexes its input signal into two demultiplexed output signals. Its first output provides signals with modulation D to receiver 24 on line 60. The second output provides signals with modulation C to receiver 22 on line 58.
- Receiver 24 generates a feedback signal related to the intensity of received signal at modulation D and routes the feedback signal to a second processor 28 on line 40.
- the processor 28 generates a bias control signal on line 51 used to adjust the bias input of modulator 16 and a phase control signal on line 50 used to adjust the RF input of modulator 16.
- the phase control signal is applied to the phase shifter 36 to adjust the phase of the 10 Gb/sec clock signal recovered by receiver 24.
- the phase-shifted clock signal is applied to the RF input of modulator 16.
- the bias control signal and phase control signals are adjusted to maximize the intensity of the modulation D signal at receiver 24.
- the first modulator 12 is set up via feedback control to partially demultiplex the incoming multiplexed signal into two partially demultiplexed signals.
- the first signal at the first output of the modulator 12 includes multiplexed signals of modulations A and B on line 13.
- the second signal at the second output of modulator 12 includes multiplexed signals of modulations C and D on line 15.
- the modulator 14 further demultiplexes the partially multiplexed signal on line 13 into two demultiplexed signals having modulations A and B.
- modulator 16 further demultiplexes the signal on line 15 into two demultiplexed signals having modulations C and D.
- the completely demultiplexed signals are applied to their respective receivers by modulators 14 and 16.
- the signal received at the input of the modulator 12 is a 40Gb/s signal, being the time-multiplexed composite of the four individual lOGb/s signals.
- the modulator 12 demultiplexes this composite signal into two 20Gb/s signals, each of which is applied to one of modulators 14 and 16.
- Each of the modulators 14 and 16 further demultiplexes its incoming 20Gb/s signal into a pair of lOGb/s signals to complete the demultiplexing of the multiplexed input signal.
- the demultiplexing of the input signal occurs in multiple stages, in this case, two stages.
- FIG. 3 contains a schematic flowchart which illustrates the logical flow of a turn-on procedure for the system of the invention in accordance with the invention. Referring to FIG. 3, in a first step 200, a signal having only modulation A is turned on and applied to the input 8 of the system 10.
- step 202 the control signals generated by the processor 26 and applied to lines 48 and 49 are adjusted to adjust the RF and bias inputs, respectively, to the modulator 14. These signals are adjusted to maximize the power of the modulation A signal received at the receiver 18. When this power is maximized, modulator 14 is locked in the correct state. It will route all modulation A power to receiver 18 and other power to receiver 20.
- step 204 the control signals generated by the processor 26 and applied to lines 52 and 55 are adjusted to adjust the RF and bias inputs, respectively, to the modulator 12. These signals are adjusted to further maximize the power of the modulation A signal received at the receiver 18. When this power is maximized, modulator 12 is locked in the correct state. It will route signals with power at modulation A and B on line 13 to modulator 14 and other signals to modulator 16 on line 15.
- step 206 a signal with modulation D power is turned on and applied to the system input 8. Because modulator 12 is already locked in the correct state, this modulation D signal will automatically be routed to the modulator 16 on line 15.
- step 208 the control signals generated by the processor 28 and applied to lines 50 and 51 are adjusted to adjust the RF and bias inputs, respectively, to the modulator 16. These signals are adjusted to maximize the power of the modulation D signal received at receiver 24. When this power is maximized, modulator 16 is locked in the correct state. It will route signals with power at modulation D on line 60 and all other signals, e.g., signals with power at modulation C, to receiver 22.
- step 210 signals with modulations B and C are turned on and applied to system input 8. Because all of the modulators 12, 14 and 16 are set up and locked in their correct states, signals with these remaining two modulations are routed automatically to their respective appropriate receivers. That is, signals with modulation B are routed to receiver 20, and signals with modulation C are routed to receiver 22.
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Optical Communication System (AREA)
- Time-Division Multiplex Systems (AREA)
Abstract
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Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU2001267089A AU2001267089A1 (en) | 2000-06-15 | 2001-06-14 | Apparatus and method for demultiplexing a time multiplexed signal |
EP01944704A EP1295423A2 (en) | 2000-06-15 | 2001-06-14 | Apparatus and method for demultiplexing a time multiplexed signal |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US59445400A | 2000-06-15 | 2000-06-15 | |
US09/594,454 | 2000-06-15 |
Publications (2)
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WO2001097426A2 true WO2001097426A2 (en) | 2001-12-20 |
WO2001097426A3 WO2001097426A3 (en) | 2003-01-16 |
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Application Number | Title | Priority Date | Filing Date |
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PCT/US2001/040968 WO2001097426A2 (en) | 2000-06-15 | 2001-06-14 | Apparatus and method for demultiplexing a time multiplexed signal |
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EP (1) | EP1295423A2 (en) |
AU (1) | AU2001267089A1 (en) |
WO (1) | WO2001097426A2 (en) |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0849906A2 (en) * | 1996-12-19 | 1998-06-24 | Fujitsu Limited | Optical time division demultiplexing apparatus and demultiplexed signal switching method as well as optical time division multiplex transmission system |
US5909297A (en) * | 1994-08-02 | 1999-06-01 | Fujitsu Limited | Drift compensating circuit for optical modulators in an optical system |
US5926297A (en) * | 1996-09-03 | 1999-07-20 | Fujitsu Limited | Optical modulating device and optical modulating method |
-
2001
- 2001-06-14 EP EP01944704A patent/EP1295423A2/en not_active Withdrawn
- 2001-06-14 AU AU2001267089A patent/AU2001267089A1/en not_active Abandoned
- 2001-06-14 WO PCT/US2001/040968 patent/WO2001097426A2/en not_active Application Discontinuation
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5909297A (en) * | 1994-08-02 | 1999-06-01 | Fujitsu Limited | Drift compensating circuit for optical modulators in an optical system |
US5926297A (en) * | 1996-09-03 | 1999-07-20 | Fujitsu Limited | Optical modulating device and optical modulating method |
EP0849906A2 (en) * | 1996-12-19 | 1998-06-24 | Fujitsu Limited | Optical time division demultiplexing apparatus and demultiplexed signal switching method as well as optical time division multiplex transmission system |
Non-Patent Citations (2)
Title |
---|
ELLIS A D ET AL: "FULL 10 * 10GBIT/S OTDM DATA GENERATION AND DEMULTIPLEXING USING ELECTROABSORPTION MODULATORS" JOURNAL OF PHARMACEUTICAL SCIENCES, AMERICAN PHARMACEUTICAL ASSOCIATION. WASHINGTON, US, vol. 88, no. 11, November 1999 (1999-11), pages 1766-1767, XP000853383 ISSN: 0022-3549 * |
MOODIE D G ET AL: "DISCRETE ELECTROABSORPTION MODULATORS WITH ENHANCED MODULATION DEPTH" JOURNAL OF LIGHTWAVE TECHNOLOGY, IEEE. NEW YORK, US, vol. 14, no. 9, 1 September 1996 (1996-09-01), pages 2035-2043, XP000630320 ISSN: 0733-8724 * |
Also Published As
Publication number | Publication date |
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WO2001097426A3 (en) | 2003-01-16 |
EP1295423A2 (en) | 2003-03-26 |
AU2001267089A1 (en) | 2001-12-24 |
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