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PDM-Nyquist-32QAM for 450-Gb/s Per-channel WDM Transmission on the 50GHz ITU-T Grid
Xiang Zhou, Lynn Nelson, Peter Magill, Rejoy Isaac, Benyuan Zhu, David W. Peckham, Peter I. Borel, Kenneth Carlson
IEEE/OSA J. Lightwave TEchnology,
2012.
[DOC]
[BIB]
IEEE Copyright
This version of the work is reprinted here with permission of IEEE for your personal use. Not for redistribution. The definitive version was published in IEEE/OSA J. Lightwave TEchnology. , 2012-02-15
{We discuss the generation and transmission of 450Gb/s wavelength-division multiplexed (WDM) channels over the 50GHz ITU-T grid at a net spectral efficiency of 8.4b/s/Hz, which is, to our best knowledge, the highest spectral efficiency demonstrated for WDM systems at 400Gb/s and beyond. This result is accomplished by the use of Nyquist-shaped, polarization-division-multiplexed (PDM) 32-quadrature amplitude modulation (QAM) and both pre- and post-transmission digital equalization. To overcome the limitation of available digital-to-analog converter bandwidth, a novel method is introduced for the generation of the five-subcarriers of the 450Gb/s signal. Nearly ideal Nyquist pulse-shaping (roll-off factor =0.01) enables guard bands of only 200MHz between subcarriers. To mitigate the narrow optical filtering effects from the 50GHz-grid reconfigurable optical add-drop multiplexer (ROADM), a broadband optical pulse-shaping method has been proposed and demonstrated. By combined use of electrical and optical shaping techniques, transmission of 5�450Gb/s PDM-Nyquist 32QAM on the 50GHz grid over 800km and one 50GHz-grid ROADM has been successfully demonstrated.}
4000km Transmission of 50GHz spaced, 10x494.85-Gb/s Hybrid 32-64QAM using Cascaded Equalization and Training-Assisted Phase Recovery
Xiang Zhou, Lynn Nelson, Peter Magill, Rejoy Isaac, B. Zhu, D. W. Peckham, P. Borel, K. Carlson
OSA (Optical Society of America),
2012.
[DOC]
[BIB]
Optical Society of America Copyright
The definitive version was published in 2012. , 2012-03-07
{Employing time-domain hybrid QAM, training-assisted phase recovery and cascaded equalization, we successfully transmitted ten 494.85Gbit/s PDM-32/64QAM DWDM signals at 8.25b/s/Hz net spectral efficiency (SE) over 40x100km, achieving a record terrestrial SE.distance product of 33000 bit.km/s/Hz}
1200km Transmission of 50GHz spaced, 5x504-Gb/s PDM-32-64 hybrid QAM using Electrical and Optical Spectral Shaping
Xiang Zhou, Lynn Nelson, Rejoy Isaac, Peter Magill, P. Borel B. Zhu, K. Carlson
OFC 2012 conference proceeding,
2012.
[DOC]
[BIB]
Optical Society of America Copyright
The definitive version was published in OFC 2012 conference proceeding. , 2012-03-04
{Employing a time-domain hybrid QAM and electrical and optical shaping, we successfully transmitted five 504Gbits/s PDM-32/64QAM DWDM signals over a record 12x100km reach (for WDM SE>4b/s/Hz) and one 50GHz-grid ROADM at a net SE 8.4b/s/Hz. }
Supermodes for Optical Transmission
Xiang Zhou, Cen Xia, Neng Bai, Guifang Li
Optics Express (OSA Journal paper),
2011.
[DOC]
[BIB]
Optical Society of America Copyright
The definitive version was published in Optics Express (OSA Journal paper). , 2011-08-31
{In this paper, the concept of supermode is introduced for long-distance optical transmission systems. The supermode uses the strong crosstalk between the cores of a multi-core fiber. The strong coupling is obtained by a coupled multi-core fiber in which the core to core distance is much shorter than the conventional multi-core fiber. The use of supermodes leads to a larger mode effective area and higher mode density than conventional multi-core fiber. The simulation results showed lower modal dependent loss, mode coupling and differential modal group delay than step-index few-mode fiber. These properties make the new coupled multi-core fiber design a good candidate for both spatial division multiplexing and single-mode operation}
Selective post-compensation of nonlinear impairments in polarization-division multiplexed WDM systems with different channel granularities
Xiang Zhou, Eduardo F. Mateo, Guifang Li
IEEE Quantum Electronics,
2011.
[BIB]
{Selective post-compensation of nonlinear impairments is investigated for polarization-division multiplexed WDM systems. A coupled system of nonlinear partial differential equations, derived from the Manakov equations, is used for digital backward propagation. Three WDM systems with different channel granularities have been simulated to evaluate the performance and computational load of vector-DBP when different inter- and/or intra-channel effects are compensated. }
Research Highlights: Optical Systems Research at AT&T Labs
Martin Birk, Mikhail Brodsky, Mark Feuer, Patrick Iannone, Peter Magill, Jonathan Nagel, Lynn Nelson, Kenneth Reichmann, Sheryl Woodward, Xiang Zhou
IEEE Photonics Newsletter,
2011.
[PDF]
[BIB]
IEEE Copyright
This version of the work is reprinted here with permission of IEEE for your personal use. Not for redistribution. The definitive version was published in IEEE Photonics Newsletter. , 2011-07-01
{}
Low-Complexity Blind Phase Recovery for Coherent Receivers Using QAM Modulation
Xiang Zhou, Yifan Sun
OFC 2011 conference proceeding,
2011.
[DOC]
[BIB]
The Optical Society of America Copyright
The definitive version was published in proceedings of OFC 2011 (Optical Society of America). , 2011-03-08, http://www.ofcnfoec.org/
{We propose a new hybrid PLL/ML phase estimation method for low-complexity blind phase recovery for M-QAM modulation. The linewidth tolerance of the proposed method is more than one order of magnitude better than PLL-only method}
Fiber Nonlinearity Management � from Carrier Perspective
Xiang Zhou, Guifang Eduardo F. Mateo
OFCNFOEC 2010 conference publication,
2011.
[DOC]
[BIB]
Optical Society of America Copyright
The definitive version was published in proceedings of OFC 2011 (Optical Society of America). , 2011-03-06, http://www.ofcnfoec.org/
{Technologies toward fiber nonlinearity management for spectrally-efficient high-speed optical transmission systems have been discussed from carrier perspective. While optimal electrical dispersion management remains an effective method, new ultra-low-nonlinearity fiber might be needed in the future. }
Electronic phase conjugation for impairment compensation in fiber communication systems
Xiang Zhou, Eduardo F. Mateo, Guifang Li
OFCNFOEC 2011 conference proceeding,
2011.
[LINK]
[BIB]
Optical Society of America (OSA) Copyright
The definitive version was published in proceedings of OFC 2011 (Optical Society of America). , 2011-03-06, http://www.ofcnfoec.org/
{Electronic phase conjugation is proposed for nonlinearity compensation in fiber communications. Mid-link coherent detection and I/Q modulation can be used to implement phase conjugation. Significant performance improvement can be achieved in WDM multi-rate systems.}
8X450-Gb/s, 50-GHz-Spaced, PDM-32QAM transmission over 400km and one 50GHz-grid ROADM
Xiang Zhou, Lynn Nelson, Peter Magill, Benuan Zhu, D. W. Peckham, Rejoy Isaac
Optical Society of America (OSA),
2011.
[DOC]
[BIB]
Optical Society of America Copyright
The definitive version was published in Optical Fiber Conference, 2011. , 2011-03-08, http://www.osa.org/
{Employing Nyquist-pulse-shaped PDM-32QAM modulation and both pre- and post-transmission digital equalization, we demonstrate 50GHz-spaced, 8X450Gbits/s DWDM transmission over 4X100km of ultra-large-area fiber and one 50GHz-grid WSS-based ROADM at 8.37b/s/Hz spectral efficiency.}
800km Transmission of 5x450-Gb/s PDM-32QAM on the 50GHz Grid using Electrical and Optical Spectral Shaping
Xiang Zhou, Lynn Nelson, Peter Magill, Rejoy Isaac, B. Zhu, D. W. Peckham, P. Borel, K. Carlson
ECOC 2011 conference proceeding,
2011.
[PDF]
[BIB]
Optical Society of America Copyright
The definitive version was published in ECOC 2011 conference proceeding. , 2011-09-18, http://www.ecoc2011.org
{We report 8x100km transmission of five 450Gbits/s PDM-32QAM DWDM signals over ultra-large-area fiber and one 50GHz-grid WSS-based ROADM at 8.4b/s/Hz spectral efficiency, enabled by the combined use of electrical and optical spectral shaping techniques}
64-Tb/s, 8b/s/Hz, PDM-36QAM Transmission over 320km Using Both Pre- and Post-Transmission Digital Signal Processing
Xiang Zhou, Lynn Nelson, Peter Magill, Martin Birk, Yin Shao Ting Wang Jianjun Yu, Peter. I. Borel Peter Magill
IEEE Journal of Lightwave Technology ,
2011.
[BIB]
{We report the successful transmission of 64Tb/s capacity (640107Gb/s in 12.5GHz channel spacing) over 320km reach utilizing the regular 8-THz C+L-band bandwidth at a spectral efficiency of 8bit/s/Hz, the highest spectral efficiency demonstrated through a full WDM transmission experiment. Such a result is accomplished by the use of raised-cosine pulse-shaped PDM-36QAM modulation, both pre- and post-transmission digital equalization and ultra-large-area fiber. We discuss in detail the used digital modulation technology and signal processing algorithms, with a special emphasis on a newly proposed linewidth-tolerant two-stage feed-forward carrier phase recovery algorithm that is implemented at the coherent receiver. }
Research Web Site, Feature article July 2010: Manipulating Lightwaves to Deliver More Data
Xiang Zhou, Farheen Masood
AT&T Labs Research Web site http://www.research.att.com,
2010.
[BIB]
{�For an electrical engineer specializing in communications, there�s no better place to intern than AT&T Research. Here there�s state of the art equipment, and highly experimental ideas can have real world application.�}
Method And Apparatus For Generating 8-QAM-Modulated Optical Signal,
December 13, 2011
A system and method for producing an 8-QAM-modulated signal are disclosed. The methodology, in an exemplary expedient, generally comprises splitting light from a CW laser into two parts; modulating the first part with a first signal and modulating the second part with a second signal; phase shifting the modulated second part by about .pi./4; combining the modulated first part with the phase shifted and modulated second part to produce a four-level modulated signal; and phase modulating the four-level modulated signal with a third signal with a phase modulation of (0, .pi./2). Several variations of this method are described herein.
Methods And Apparatus For Generating 16-QAM-Modulated Optical Signal,
December 6, 2011
A system and method for producing a 16-QAM-modulated signal are disclosed. The methodology, in an exemplary expedient, generally comprises splitting light from a CW laser into two parts; modulating the first part with a first signal and modulating the second part with a second signal; phase shifting the modulated second part by about .pi./2; combining the modulated first part with the phase shifted and modulated second part to produce a four-level modulated signal; phase modulating the four-level modulated signal with a third signal with a phase modulation of about (0, .pi./2) to produce an 8-QAM-modulated signal, and thereafter modulating that signal with a fourth signal with a phase-modulation of about (0, .pi.) to produce the 16-QAM-modulated signal.
Method For Improving The Performance Of Phase-Modulated Communication System In An Optical Network,
July 19, 2011
A method and system for improving the performance of a differential-phase modulated optical communication system is disclosed. The system comprises a demodulator having a tunable element to adjust the free-spectral range (FSR) thereof, and a tunable phase shifter to adjust a frequency of a signal passing therethrough.
Feedback Dynamic Gain Control For A WDM System Employing Multi-Wavelength Pumped Raman Fiber Amplifiers,
March 29, 2011
An improved feedback-based dynamic gain control technique for a WDM system employing multi-wavelength-pumped Raman fiber amplifiers (RFAs) is proposed, in which only one feedback or feed-forward signal is required for the control of multiple Raman pumps. Compared to the traditional method requiring multiple feedback signals for multiple pumps, the proposed method results in substantial simplification of the control circuit and also exhibits faster control speed. Moreover, the proposed method allows use of the total signal gain as the feedback signal, which is more robust against polarization-related issues than the traditional method using signal powers at several different channels as the feedback signals. The improved technique has advantage for dynamic gain control in a backward-pumped distributed RFA because the feedback signal may be detected right after the RFA. For feed-forward, a telemetry channel may be used to send the feed-forward signal to a feed-forward control circuit for the multiple Raman pumps. In addition, the feed-forward control technique and the feedback control technique may be used together to achieve better performance than using each of them separately to control multiple Raman pumps. Polarization-related issues may be reduced by utilizing amplified spontaneous emission (ASE) noise as the feedback signal for a feedback-based gain control circuit for the RFA.
Fast Dynamic Gain Control In A Bidirectionally-Pumped Raman Fiber Amplifier,
March 1, 2011
The present invention provides methods and apparatuses for controlling a gain of a bidirectionally-pumped Raman fiber amplifier having both forward optical pumps and backward optical pumps. The overall gain is controlled by adjusting the forward optical pumps, while the power levels of the backward optical pumps are essentially fixed. Gain circuitry operates in an opened loop configuration and uses a predetermined function relating a power variation of at least one wavelength region with a pump power adjustment for at least one forward optical pump. Two approximate linear relationships between the input signal power variations and the required pump power adjustments are utilized in controlling the Raman fiber amplifier. Each approximate linear relationship includes at least one linear coefficient that relates a power variation for a specific wavelength region and a power adjustment of a specific Raman pump.
Method and Apparatus For Adjusting For Polarization-Induced, Optical Signal Transients,
August 3, 2010
The invention includes methods and apparatuses to adjust an optical signal transmitted through an optical amplifier, such as in a wavelength division multiplexed optical network. The methods and apparatus of the invention calculate polarization effects which cause degradation to the optical signal. A measurement of the polarization-related degradation of an optical signal is calculated by using at least one reference signal. In some embodiments of the invention, the reference signal is depolarized or has scrambled polarizations. The invention is typically used in long-haul optical networks.
Multi-Band Hybrid SOA-Raman Amplifer For CWDM,
June 29, 2010
A multi-band hybrid amplifier is disclosed for use in optical fiber systems. The amplifier uses Raman laser pumps and semiconductor optical amplifiers in series to produce a relatively level gain across the frequency range of interest. Multiple Raman pumps are multiplexed before coupling into the fiber. The Raman amplified optical signal may be demultiplexed and separately amplified by the SOAs before re-multiplexing. Gain profiles of the Raman pumps and the SOAs are selected to compensate for gain tilt and to alleviate the power penalty due to cross-gain modulation in the SOAs. The disclosed hybrid amplifier is especially useful in coarse wavelength division multiplexing (CWDM) systems.
Multi-Band Hybrid SOA-Raman Amplifer For CWDM,
June 15, 2010
A multi-band hybrid amplifier is disclosed for use in optical fiber systems. The amplifier uses Raman laser pumps and semiconductor optical amplifiers in series to produce a relatively level gain across the frequency range of interest. Multiple Raman pumps are multiplexed before coupling into the fiber. The Raman amplified optical signal may be demultiplexed and separately amplified by the SOAs before re-multiplexing. Gain profiles of the Raman pumps and the SOAs are selected to compensate for gain tilt and to alleviate the power penalty due to cross-gain modulation in the SOAs. The disclosed hybrid amplifier is especially useful in coarse wavelength division multiplexing (CWDM) systems.
Fast Dynamic Gain Control In An Optical Fiber Amplifier,
March 2, 2010
The present invention provides methods and apparatuses for controlling a gain of an optical fiber amplifier. Gain circuitry operates in an opened loop configuration and uses a predetermined function relating a power variation of at least one wavelength region with a pump power adjustment for at least one optical pump. Two approximate linear relationships between the input signal power variations and the required pump power adjustments are utilized in controlling the Raman fiber amplifier. Each approximate linear relationship includes at least one linear coefficient that relates a power variation for a specific wavelength region and a power adjustment of a specific Raman pump. The dynamic gain control technique is applicable to an Erbium-doped fiber/waveguide amplifier. Also, a dynamic gain control technique controls a backward-pumped Raman amplifier, in which the power variation is determined at one geographical location and the optical pumps are controlled at another geographical location.
Method, Apparatus And System For Cost-Effective Optical Transmission With Fast Raman Tilt Transient Control,
December 22, 2009
A method for cost-effective optical transmission with fast Raman tilt or other transient event control uses a combination of Erbium-doped fiber amplifiers (EDFAs) and Raman fiber amplifiers (RFAs), where EDFAs are used as the primary optical amplifiers to compensate the span loss while the RFA (advantageously a forward-pumped RFA) is used only in some specific spans with a feed-forward control circuit serving as a fast Raman tilt transient compensator, the RFA also serving as an optical amplifier. A long haul optical transmission system using feed-forward controlled RFA's periodically spaced along its length, for example, when add-drop multiplexing is used, makes full use of the economics of EDFAs and the fast tilt transient control capability of a RFA enabled by an adjustable speed feed-forward or feed-back control technique. In addition, the introduced RFA also performs a dynamic gain equalization function which may eliminate the need or at least reduce the number of standalone dynamic gain equalizers which are required for an ultra-long-haul (ULH) WDM system to compensate for tilt. The invention is also applicable to the common EDFA/Raman hybrid systems and to some all-Raman systems where backward-pumped RFAs are used at each span to enhance Raman transient event control speed.
Fast Dynamic Gain Control In An Optical Fiber Amplifier,
June 30, 2009
The present invention provides methods and apparatuses for controlling a gain of an optical fiber amplifier. Gain circuitry operates in an opened loop configuration and uses a predetermined function relating a power variation of at least one wavelength region with a pump power adjustment for at least one optical pump. Two approximate linear relationships between the input signal power variations and the required pump power adjustments are utilized in controlling the Raman fiber amplifier. Each approximate linear relationship includes at least one linear coefficient that relates a power variation for a specific wavelength region and a power adjustment of a specific Raman pump. The dynamic gain control technique is applicable to an Erbium-doped fiber/waveguide amplifier. Also, a dynamic gain control technique controls a backward-pumped Raman amplifier, in which the power variation is determined at one geographical location and the optical pumps are controlled at another geographical location.
Fast Dynamic Gain Control In An Optical Fiber Amplifier,
June 30, 2009
The present invention provides methods and apparatuses for controlling a gain of an optical fiber amplifier. Gain circuitry operates in an opened loop configuration and uses a predetermined function relating a power variation of at least one wavelength region with a pump power adjustment for at least one optical pump. Two approximate linear relationships between the input signal power variations and the required pump power adjustments are utilized in controlling the Raman fiber amplifier. Each approximate linear relationship includes at least one linear coefficient that relates a power variation for a specific wavelength region and a power adjustment of a specific Raman pump. The dynamic gain control technique is applicable to an Erbium-doped fiber/waveguide amplifier. Also, a dynamic gain control technique controls a backward-pumped Raman amplifier, in which the power variation is determined at one geographical location and the optical pumps are controlled at another geographical location.
Multi-band hybrid SOA-raman amplifier for CWDM,
December 9, 2008
A multi-band hybrid amplifier is disclosed for use in optical fiber systems. The amplifier uses Raman laser pumps and semiconductor optical amplifiers in series to produce a relatively level gain across the frequency range of interest. Multiple Raman pumps are multiplexed before coupling into the fiber. The Raman amplified optical signal may be demultiplexed and separately amplified by the SOAs before re-multiplexing. Gain profiles of the Raman pumps and the SOAs are selected to compensate for gain tilt and to alleviate the power penalty due to cross-gain modulation in the SOAs. The disclosed hybrid amplifier is especially useful in coarse wavelength division multiplexing (CWDM) systems.
Method, apparatus and system for cost effective optical transmission with fast Raman tilt transient control,
November 4, 2008
A method for cost-effective optical transmission with fast Raman tilt or other transient event control uses a combination of Erbium-doped fiber amplifiers (EDFAs) and Raman fiber amplifiers (RFAs), where EDFAs are used as the primary optical amplifiers to compensate the span loss while the RFA (advantageously a forward-pumped RFA) is used only in some specific spans with a feed-forward control circuit serving as a fast Raman tilt transient compensator, the RFA also serving as an optical amplifier. A long haul optical transmission system using feed-forward controlled RFA's periodically spaced along its length, for example, when add-drop multiplexing is used, makes full use of the economics of EDFAs and the fast tilt transient control capability of a RFA enabled by an adjustable speed feed-forward or feed-back control technique. In addition, the introduced RFA also performs a dynamic gain equalization function which may eliminate the need or at least reduce the number of standalone dynamic gain equalizers which are required for an ultra-long-haul (ULH) WDM system to compensate for tilt. The invention is also applicable to the common EDFA/Raman hybrid systems and to some all-Raman systems where backward-pumped RFAs are used at each span to enhance Raman transient event control speed.
Fast dynamic gain control in a bidirectionally-pumped Raman fiber amplifier,
October 14, 2008
The present invention provides methods and apparatuses for controlling a gain of a bidirectionally-pumped Raman fiber amplifier having both forward optical pumps and backward optical pumps. The overall gain is controlled by adjusting the forward optical pumps, while the power levels of the backward optical pumps are essentially fixed. Gain circuitry operates in an opened loop configuration and uses a predetermined function relating a power variation of at least one wavelength region with a pump power adjustment for at least one forward optical pump. Two approximate linear relationships between the input signal power variations and the required pump power adjustments are utilized in controlling the Raman fiber amplifier. Each approximate linear relationship includes at least one linear coefficient that relates a power variation for a specific wavelength region and a power adjustment of a specific Raman pump.
Multi-band hybrid SOA-raman amplifier for CWDM,
March 11, 2008
A multi-band hybrid amplifier is disclosed for use in optical fiber systems. The amplifier uses Raman laser pumps and semiconductor optical amplifiers in series to produce a relatively level gain across the frequency range of interest. Multiple Raman pumps are multiplexed before coupling into the fiber. The Raman amplified optical signal may be demultiplexed and separately amplified by the SOAs before re-multiplexing. Gain profiles of the Raman pumps and the SOAs are selected to compensate for gain tilt and to alleviate the power penalty due to cross-gain modulation in the SOAs. The disclosed hybrid amplifier is especially useful in coarse wavelength division multiplexing (CWDM) systems.
Fast dynamic gain control in cascaded Raman fiber amplifiers,
October 9, 2007
The present invention provides methods and apparatuses for controlling a gain of a bidirectionally-pumped Raman fiber amplifier having both forward optical pumps and backward optical pumps. The overall gain is controlled by adjusting the forward optical pumps, while the power levels of the backward optical pumps are essentially fixed. Gain circuitry operates in an opened loop configuration and uses a predetermined function relating a power variation of at least one wavelength region with a pump power adjustment for at least one forward optical pump. Two approximate linear relationships between the input signal power variations and the required pump power adjustments are utilized in controlling the Raman fiber amplifier. Each approximate linear relationship includes at least one linear coefficient that relates a power variation for a specific wavelength region and a power adjustment of a specific Raman pump.
Fast dynamic gain control in cascaded Raman fiber amplifiers,
October 2, 2007
The present invention provides methods and apparatuses for controlling a gain of a bidirectionally-pumped Raman fiber amplifier having both forward optical pumps and backward optical pumps. The overall gain is controlled by adjusting the forward optical pumps, while the power levels of the backward optical pumps are essentially fixed. Gain circuitry operates in an opened loop configuration and uses a predetermined function relating a power variation of at least one wavelength region with a pump power adjustment for at least one forward optical pump. Two approximate linear relationships between the input signal power variations and the required pump power adjustments are utilized in controlling the Raman fiber amplifier. Each approximate linear relationship includes at least one linear coefficient that relates a power variation for a specific wavelength region and a power adjustment of a specific Raman pump.
Fast dynamic gain control in an optical fiber amplifier,
November 28, 2006
The present invention provides methods and apparatuses for controlling a gain of an optical fiber amplifier. Gain circuitry operates in an opened loop configuration and uses a predetermined function relating a power variation of at least one wavelength region with a pump power adjustment for at least one optical pump. Two approximate linear relationships between the input signal power variations and the required pump power adjustments are utilized in controlling the Raman fiber amplifier. Each approximate linear relationship includes at least one linear coefficient that relates a power variation for a specific wavelength region and a power adjustment of a specific Raman pump. The dynamic gain control technique is applicable to an Erbium-doped fiber/waveguide amplifier. Also, a dynamic gain control technique controls a backward-pumped Raman amplifier, in which the power variation is determined at one geographical location and the optical pumps are controlled at another geographical location.
Method and apparatus for providing a broadband raman amplifier with improved noise performance,
May 16, 2006
A method and apparatus is presented which reduces noise degradation in the shorter wavelength band by using modulation of one/multiple pumps plus multiple-order Raman amplification. Such a scheme is very suitable for the case of SSMF fiber where pump--pump induced four-wave mixing (FWM) effects are negligible. Further, a group Time Domain Multiplexing (TDM) configuration is provided to simultaneously reduce the amplified spontaneous emission (ASE) noise and pump--pump induced FWM effects for the case of NZ-DSF fiber.
Method And Apparatus For Providing A Broadband Raman Amplifier With Improved Noise Performance,
November 2, 2004
A method and apparatus is presented which reduces noise degradation in the shorter wavelength band by using modulation of one/multiple pumps plus multiple-order Raman amplification. Such a scheme is very suitable for the case of SSMF fiber where pump-pump induced four-wave mixing (FWM) effects are negligible. Further, a group Time Domain Multiplexing (TDM) configuration is provided to simultaneously reduce the amplified spontaneous emission (ASE) noise and pump-pump induced FWM effects for the case of NZ-DSF fiber.
