Multiwavelength mode-locked dense wavelength division multiplexed optical communication systems

• US 6,014,237 A
• Filed: 11/03/1998
• Issued: 01/11/2000
• Est. Priority Date: 06/01/1998
• Status: Expired due to Fees

• Current Assignee: Sarnoff Corporation (SRI International, Inc.)
• Original Assignee: Sarnoff Corporation (SRI International, Inc.)
• Inventors: Connolly, John Charles, Abeles, Joseph Hy, Stephens, William Edward, Camisa, Raymond Louis
• Primary Examiner(s): NEGASH, KINFE MICHAEL
• Application Number:
  US09/184,906
• Time in Patent Office: 434 Days
• Field of Search: 359/123-124, 359/133, 359/130, 359/132, 359/173, 359/180, 372/18
• US Class Current: 398/87
• CPC Class Codes: H01S 5/065 Mode locking; Mode suppression; Mode selection ; Self pulsating
• CPC Class Codes: H01S 5/0657 Mode locking, i.e. generation of pulses at a frequency corresponding to a roundtrip in the cavity
• CPC Class Codes: H01S 5/1096 in a single cavity
• CPC Class Codes: H01S 5/1215 Multiplicity of periods
• CPC Class Codes: H01S 5/146 using a fiber as external cavity
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems
• CPC Class Codes: H04J 14/0223 Conversion to or from optical TDM
• CPC Class Codes: H04J 14/08 Time-division multiplex systems
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 2011/0079 Operation or maintenance aspects

Abstract

A multi-wavelength mode-locked dense wavelength division multiplexed (MWML-DWDM) optical transmission method and system including a MWML-DWDM optical transmitter having a multiwavelength mode-locked (MWML) laser which generates a wavelength-ordered repetitive periodic (WORP) sequence of discrete optical pulses for modulation with data carried by at least one electronic carrier. Signals from multiple telecommunications transmission interfaces are multiplexed together by a high speed electronic time domain multiplexer to form a single multiplexed high speed digital transmission stream that is encoded onto the optical pulse stream output by the MWML-DWDM optical transmitter by an optical modulator so as to provide multiple channels of information carried on a DWDM data stream over an optical fiber to a receiver where the data is received and decoded. A single MWML-DWDM optical transmitter and a single modulator may replace the numerous laser sources and associated modulators used in conventional WDM optical transmission systems. Wavelength usage may be further maximized by combining the outputs of several MWML-DWDM optical transmitters in the frequency domain using optical combiners or in the time domain using time division multiplexing techniques according to which DWDM wavelengths may be used more than once during a WORP-frame but only once during a pulse-frame. A single MWML laser source can provide hundreds of optical carriers.

Claims

1. A wavelength ordered repetitive periodic dense wavelength division multiplexed (WORP-DWDM) optical source, comprising:

a multiwavelength mode-locked (MWML) laser source including a semiconductor optical amplifier (SOA) disposed in a cavity of said MWML laser source, said SOA being actively driven by a radio frequency (RF) signal and emitting periodic pulses within a plurality of discrete wavelength bands simultaneously at a port of said MWML laser source, where the RF signal oscillates at a frequency whereby one of said frequency and a sub-harmonic of said frequency substantially equals the inverse of the round trip travel time of pulses circulating within a cavity of said MWML laser source; and

a temporal dispersion element which time shifts said plurality of wavelengths by differential wavelength-dependent delays so as to transform pulses emitted by said MWML laser source into a wavelength ordered repetitive periodic (WORP) sequence of optical pulses.

2. A WORP-DWDM optical source as in claim 1, wherein said MWML laser source comprises an angled-stripe SOA and a RF source which applies said RF signal to said SOA.

3. A WORP-DWDM optical source as in claim 1, wherein said temporal dispersion element comprises one of a temporal dispersion filter and a dispersive fiber grating.

4. A multi-wavelength mode-locked dense wavelength division multiplexed (MWML-DWDM) optical transmitter, comprising:

a multiwavelength mode-locked (MWML) laser source comprising a semiconductor optical amplifier (SOA) disposed in a cavity of said MWML laser source, said SOA being actively driven by a radio frequency (RF) signal and emitting periodic pulses within a plurality of discrete wavelength bands simultaneously at a port of said MWML laser source, where the RF signal oscillates at a frequency whereby one of said frequency and a sub-harmonic of said frequency substantially equals the inverse of the round trip travel time of pulses circulating within a cavity of said MWML laser source;

a temporal dispersion element which time shifts said plurality of wavelengths by differential wavelength-dependent delays so as to transform pulses emitted by said MWML laser source into a wavelength ordered repetitive periodic (WORP) sequence of optical pulses; and

an optical modulator which modulates an electronic digital data stream onto individual wavelengths in said WORP sequence.

5. A MWML-DWDM optical transmitter as in claim 4, further comprising an optical amplifier which amplifies an output of said optical modulator.

6. A MWWL-DWDM optical transmitter as in claim 4, further comprising an etalon filter which filters an output of said optical modulator so as to narrow a spectrum of each individual wavelength from said optical modulator so as to mitigate wavelength dispersion and to lengthen pulses beyond the duration of their respective pulse-frames, where the pulse-frames are the time intervals allocated within a WORP pulse sequence to transmission of a single pulse.

7. A MWML-DWDM optical transmitter as in claim 4, further comprising a digital electronic time domain multiplexer (EDTM) which drives a multiplicity of discrete data signals into said optical modulator for modulation onto respective wavelengths in said WORP sequence.

8. A MWML-DWDM optical transmitter as in claim 7, wherein said ETDM receives a plurality of discrete data signals, combines said plurality of discrete data signals into an electronic digital data stream, and synchronizes said digital data stream to said WORP sequence so as to provide said discrete data signals on respective wavelengths in said WORP sequence.

9. A multi-wavelength mode-locked dense wavelength division multiplexed (MWML-DWDM) optical transmitter, comprising:

a multiwavelength mode-locked (MWML) laser source comprising a semiconductor optical amplifier (SOA) disposed in a cavity of said MWML laser source, said SOA being actively driven by a radio frequency (RF) signal and emitting periodic pulses within a plurality of discrete wavelength bands simultaneously at a port of said MWML laser source, where the RF signal oscillates at a frequency whereby one of said frequency and a sub-harmonic of said fundamental frequency substantially equals the inverse of the round trip travel time of pulses circulating within a cavity of said MWML laser source;

a temporal dispersion element which time shifts said plurality of wavelengths by differential wavelength-dependent delays so as to transform pulses emitted by said MWML laser source into a wavelength ordered repetitive periodic (WORP) sequence of optical pulses;

a wavelength selective splitter which splits said WORP sequence of optical pulses into at least two pulse sub-sequences, each pulse sub-sequence containing a subset of wavelengths generated by said MWML laser source;

an optical modulator for each pulse sub-sequence, each optical modulator modulating a digital data stream onto each individual wavelength in a pulse sub-sequence received by the optical modulator; and

an optical combiner that combines an output from each of said optical modulators into a single multiwavelength aggregated optical data stream for transmission.

10. A MWML-DWDM optical transmitter as in claim 9, wherein each path of each separate pulse sub-sequence imposes a delay on said each pulse substream, whereby a timing of optical data substreams following combination of said outputs of said optical modulators by said optical combiner can be adjusted based on said delays.

11. A MWML-DWDM optical transmitter as in claim 9, further comprising a digital electronic time domain multiplexer (ETDM) which drives a multiplicity of discrete data signals into each of said optical modulators for modulation onto respective wavelengths in said WORP sequence.

12. A MWML-DWDM optical transmitter as in claim 11, wherein said ETDM receives a plurality of discrete data signals, combines said plurality of discrete data signals into an electronic digital data stream, and synchronizes said digital data stream to portions of said WORP optical pulse sequence applied to each of said optical modulators so as to provide said discrete data signals on respective wavelengths in said WORP sequence.

13. A MWML-DWDM optical transmitter as in claim 9, wherein said optical combiner combines said WORP sequences from each optical modulator in a time shifted temporal order such that a wavelength may be used by more than one optical modulator to transmit data so long as said wavelength is not used in the same pulse-frame, where the pulse frame is the time interval allocated within a WORP pulse sequence to transmission of a single pulse, by said more than one optical modulator.

14. A multi-wavelength mode-locked dense wavelength division multiplexed (MWML-DWDM) optical transmitter, comprising:

a plurality of multiwavelength lasers, each multiwavelength laser emitting pulses at a plurality of wavelengths simultaneously at a port of said multiwavelength laser;

a temporal dispersion element which time shifts said plurality of wavelengths by differential wavelength-dependent delays so as to transform pulses emitted by said multiwavelength lasers into a wavelength ordered repetitive periodic dense wavelength division multiplexed (WORP) sequences of optical pulses;

an optical modulator for each of said multiwavelength lasers, each optical modulator modulating a digital data stream onto each individual wavelength in said WORP sequence; and

an optical combiner which combines WORP sequences from each optical modulator into a single optical data stream for transmission.

15. A MWML-DWDM optical transmitter as in claim 14, wherein each said multiwavelength laser is a multiwavelength mode-locked (MWML) laser source including a semiconductor optical amplifier (SOA) disposed a cavity of said MWML laser source, said SOA being actively driven by a radio frequency (RF) signal and emitting periodic pulses within a plurality of discrete wavelength bands simultaneously at a port of said MWML laser source, where the RF signal oscillates at a frequency whereby one of said frequency and a frequency sub-harmonic of said frequency substantially equals the inverse of the round trip travel time of pulses circulating within a cavity of said MWML laser source.

16. A MWML-DWDM optical transmitter as in claim 14, wherein said optical combiner combines said WORP sequences from each of said plurality of optical modulators in a time shifted temporal order such that a wavelength may be used by more than one optical modulator to transmit data so long as said wavelength is not used in the same pulse-frame by said more than one optical modulator.

17. A multi-wavelength mode-locked dense wavelength division multiplexed (MWML-DWDM) optical transmission system, comprising:

a MWML-DWDM optical transmitter comprising;

a multiwavelength mode-locked (MWML) laser source including a semiconductor optical amplifier (SOA) disposed in a cavity of said MWML laser source, said SOA being actively driven by a radio frequency (RF) signal and emitting periodic pulses within a plurality of discrete wavelength bands simultaneously at a port of said MWML laser source, where the RF signal oscillates at a frequency whereby one of said frequency and a sub-harmonic of said frequency substantially equals the inverse of the round trip travel time of pulses circulating within a cavity of said MWML laser source,

a temporal dispersion element which time shifts said plurality of wavelengths by differential wavelength-dependent delays so as to transform pulses emitted by said MWML laser source into a wavelength ordered repetitive periodic (WORP) sequence of optical pulses, and

an optical modulator which modulates a digital data stream onto individual wavelengths in said WORP sequence;

an optical fiber which transmits said WORP sequence; and

a MWML-DWDM optical receiver comprising;

a DWDM filter which separates said WORP sequence into said plurality of wavelengths, and

a plurality of optical receivers which demodulate said digital data stream from each of said plurality of wavelengths.

18. A MWML-DWDM optical transmission system as in claim 17, wherein said MWML-DWDM optical transmitter further comprises a digital electronic time domain multiplexer (ETDM) which drives a multiplicity of discrete data signals into said optical modulator for modulation onto respective wavelengths in said WORP sequence.

19. A MWML-DWDM optical transmission system as in claim 18, herein said ETDM receives a plurality of discrete data signals, combines said plurality of iscrete data signals into an electronic digital data stream, and synchronizes said digital data stream to said WORP sequence so as to provide said discrete data signals on respective wavelengths in said WORP sequence.

20. A multi-wavelength mode-locked dense wavelength division multiplexed time-division multiplexed (MWML-DWDM-TDM) optical transmission system, comprising:

a MWML-DWDM optical transmitter comprising;

at least one multiwavelength laser emitting periodic pulses within a plurality of discrete wavelength bands simultaneously at a port of said multiwavelength laser,

a temporal dispersion element for each of said multiwavelength lasers, each temporal dispersion element time shifting said plurality of wavelengths by differential wavelength-dependent delays so as to transform pulses output by said multiwavelength laser into a wavelength ordered repetitive periodic (WORP) sequence of optical pulses,

an optical modulator for each of said multiwavelength lasers, each optical modulator modulating a digital data stream onto each individual wavelength in said WORP sequence, and

an optical combiner combines said WORP sequences from each optical modulator in a time shifted temporal order such that a wavelength may be used by more than one optical modulator to transmit data so long as said wavelength is not used in the same pulse-frame, where the pulse frame is the time interval allocated within a WORP pulse sequence to transmission of a single pulse, by said more than one optical modulator;

an optical fiber which transmits said combined WORP sequences; and

a MWML-DWDM-TDM optical receiver comprising;

a plurality of optical pulse-frame selectors which select optical data from at least one of a plurality of wavelengths in a particular optical pulse-frame in a received combined WORP sequence,

a plurality of DWDM filters, each DWDM filter separating the combined WORP sequences in at least one optical pulse-frame into said plurality of wavelengths, and

a plurality of optical receivers which demodulate said optical digital data streams to obtain electronic digital data streams.

21. A MWML-DWDM optical transmitter as in claim 20, wherein each said multiwavelength laser is a multiwavelength mode-locked (MWML) laser source including a semiconductor optical amplifier (SOA) disposed in a cavity of said MWML laser source, said SOA being actively driven by a radio frequency (RF) signal and emitting periodic pulses within a plurality of discrete wavelength bands simultaneously at a port of said MWML laser source, where the RF signal oscillates at a frequency whereby one of said frequency and a sub-harmonic of said frequency substantially equals the inverse of the round trip travel time of pulses circulating within a cavity of said MWML laser source.

22. A MWML-DWDM optical transmitter as in claim 20, wherein said pulse-frame selector comprises a plurality of optical switches which select respective pulse-frames and provide optical data in said respective pulse-frames for demodulation by a corresponding optical receiver.

23. A multi-wavelength mode-locked dense wavelength division multiplexed (MWML-DWDM) optical transmission method, comprising the steps of:

generating light emission by a multiwavelength laser, said light emission including periodic pulses emitted within a plurality of discrete wavelength bands simultaneously at an output of said multiwavelength laser;

time shifting pulses in said discrete wavelength bands by differential wavelength-dependent delays so as to transform pulses emitted by said multiwavelength laser into a wavelength ordered repetitive periodic (WORP) sequence; and

modulating a digital data stream onto each individual wavelength in said WORP sequence for transmission.

24. A MWML-DWDM optical transmission method as in claim 23, wherein said modulating step comprises the steps of receiving a plurality of discrete data signals, combining said plurality of discrete data signals into an electronic digital data stream, and synchronizing said digital data stream to said WORP sequence so as to provide said discrete data signals on respective wavelengths in said WORP sequence.

25. A MWML-DWDM optical transmission method as in claim 23, comprising the further step of filtering the modulated WORP sequence so as to narrow a spectrum of each individual wavelength and to mitigate wavelength dispersion and to lengthen the duration of optical pulses beyond the pulse-frame, where the pulse frame is the time interval allocated within a WORP pulse sequence to transmission of a single pulse.

26. A MWML-DWDM optical transmission method as in claim 23, wherein said modulating step comprises the steps of splitting said WORP sequence into at least two pulse sub-sequences, modulating each individual wavelength in each of said pulse sub-sequences with an optical data stream in a separate data modulator for each said pulse sub-sequences, and combining an output from each separate data modulator into a single optical data stream for transmission.

27. A MWML-DWDM optical transmission method as in claim 23, comprising the further steps of transmitting said modulated WORP sequence, separating said modulated WORP sequence into said plurality of wavelengths at a receiver, and demodulating said digital data stream from said plurality of wavelengths at said receiver.

28. A MWML-DWDM optical transmission method as in claim 23, comprising the further step of combining said WORP sequences in a time shifted temporal order such that a wavelength may be used by more than one optical modulator to transmit data so long as said wavelength is not used in the same pulse-frame, where the pulse frame is the time interval allocated within a WORP pulse sequence to transmission of a single pulse, by said more than one optical modulator.

29. A MWML-DWDM optical transmission method as in claim 28, comprising the further steps of transmitting said WORP sequence, selecting optical data from at least one of a plurality of wavelengths in a particular optical pulse-frame in the received combined WORP sequences, separating the modulated combined WORP sequences in at least one optical pulse-frame into said plurality of wavelengths, and demodulating the digital data stream.