200 S Laurel Ave - Bldg A
Middletown, NJ
ROADM System for Space Division Multiplexing With Spatial Superchannels
Mark Feuer, Lynn Nelson, Xiang Zhou, Rejoy Isaac, K. Abedin, B. Zhu, D. Marom, G. Cohen, R. Harel
OFC/NFOEC2013 conterence proceedings,
2013.
[PDF]
[BIB]
Optical Society of America Copyright
The definitive version was published in 2013. , 2013-03-17
{A two-span SDM system includes the first ROADM supporting spatial superchannels and the first cladding-pumped multicore-EDFA directly spliced to multicore transmission fiber. For 6x40x128-Gb/s SDM-WDM-PDM-QPSK transmission, BER penalties are <1.3dB in Add, Drop, and Express paths.}
Joint Digital Signal Processing Receivers for Spatial Superchannels
Mark Feuer, Lynn Nelson, Xiang Zhou, Sheryl Woodward, Rejoy Isaac, Benyuan Zhu, Thierry F. Taunay, Michael Fishteyn, John F. Fini, Man F. Yan
IEEE Photonics Technology Letters,
2012.
[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 2012. , Volume 24, Issue 21, 2012-11-01
{We discuss the advantages of spatial superchannels for future terabit networks based on space division multiplexing (SDM), and demonstrate reception of spatial superchannels by a coherent receiver utilizing joint digital signal processing (DSP). In a spatial superchannel, the SDM modes at a given wavelength are routed together, allowing simplified design of both transponders and optical routing equipment. For example, common-mode impairments can be exploited to streamline the receiver’s DSP. Our lab measurements reveal that the phase fluctuations between the cores of a multicore fiber are strongly correlated, and therefore constitute such a common-mode impairment. We have implemented master-slave phase recovery of two simultaneous 112Gbps subchannels in a 7-core fiber, demonstrating reduced processing complexity with no increase in the bit-error ratio. Furthermore, we have investigated the feasibility of applying this technique to subchannels carried on separate single-mode fibers, a potential transition strategy to evolve today’s fiber networks toward future networks using multicore fibers.}
Hole-assisted few-mode multi-core fiber for high density space-division multiplexing
Xiang Zhou, University of Santiago de Compostela. Santiago de Compostela Carlos Montero, Eduardo Mateo, Neng Bai Cen Xia, Axel Schulzgen Guifang Li Enrique Antonio-Lopez
ECOC 2012,
2012.
[PDF]
[BIB]
Optical Society of America Copyright
The definitive version was published in 2012. , 2012-09-19
{A seven-core few-mode multi-core fiber in which each core supports three spatial
modes has been designed and fabricated for the first time. The hole-assisted structure allows low crosstalk transmission of 21 spatial modes per polarization per wavelength.}
High Spectral Efficiency 400G Transmission
Xiang Zhou
ZTE Communications ,
2012.
[DOC]
[BIB]
ZTE Copyright
The definitive version was published in 2012 , 2012-03-15, http://wwwen.zte.com.cn/endata/magazine/ztecommunications
{This paper presents an overview on the generation and transmission of 450Gb/s wavelength-division multiplexed (WDM) channels over the standard 50GHz ITU-T grid at a net spectral efficiency (SE) of 8.4b/s/Hz. It is shown that the use of near ideal Nyquist pulse shaping, spectrally-efficiecnt high-order modulation format, distributed Raman amplficiation, distributed compensation of ROADM filtering effects, coherent equalization and high-coding gain forward error correction (FEC) code may enable us to operate future 400G systems over the standard 50GHz-grid optical network. }
Hardware Efficient Carrier Recovery Algorithms for Single-Carrier QAM systems
Xiang Zhou
Optical Society of America Summer Topical meeting Signal Processing in Photonic Communications (SPP,
2012.
[DOC]
[BIB]
Optical Society of America Copyright
The definitive version was published in 2012 , 2012-06-17
{This paper presents an overview on recent advancement of carrier synchronization techniques for optical systems using single-carrier quadrature-amplitude-modulation (QAM), with a special emphasis on a class of newly proposed multi-stage blind carrier recovery algorithms. }
Demonstration of Joint DSP Receivers for Spatial Superchannels
Mark Feuer, Lynn Nelson, Xiang Zhou, Sheryl Woodward, Rejoy Isaac, B. Zhu, T. F. Taunay, M. Fishteyn, J. F. Fini, M. F. Yan
IEEE Photonics Summer Topicals 2012 conference,
2012.
[PDF]
[BIB]
IEEE Copyright
The definitive version was published in 2012. , 2012-07-09
{We report lab measurements of joint digital signal processing of simultaneous 112Gbps links in a 7-core fiber. Strongly-correlated phase fluctuations between the cores permit reduced processing complexity with no increase in the bit-error ratio.}
400G WDM Transmission on the 50GHz Grid for Future Optical Networks
Xiang Zhou, Lynn Nelson
OSA/IEEE Journal of 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 2012. , 2012-10-31
{We review the recent technology advancements related to the transmission of 400Gb/s, wavelength-division-multiplexed channels for optical networks based on the standard 50GHz grid. We discuss the enabling modulation, coding, and line system technologies, as well as the existing challenges. Specifically, these technologies include time-domain hybrid 32-64 quadrature amplitude modulation, nearly ideal digital Nyquist pulse shaping, improved channel bandwidth management methods such as end-to-end carrier frequency control and distributed compensation of filtering effects arising from reconfigurable optical add-drop multiplexers, distributed Raman amplification, and powerful forward-error-correction. We demonstrate 400G transmission on the standard 50GHz grid over meaningful transmission reach for regional and metropolitan applications. However, further studies are needed to fully understand the potential for meeting the requirements of long-haul transmission applications.}
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}
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
{}
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.}
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.�}
Blind Equalization Algorithms For Adaptive Polarization Recovery And PMD Compensation,
Tue Nov 27 16:12:26 EST 2012
A device and method are disclosed for blind equalization of an optical signal to implement adaptive polarization recovery, Polarization Mode Dispersion (PMD) compensation, and residual Chromatic Dispersion (CD) compensation in a digital coherent optical communication system.
Method For Improving The Performance Of Digital Coherent Optical Receiver Using Single Ended Photo-Detection,
Tue Sep 11 16:11:49 EDT 2012
A method and system for mitigating distortion in coherent single-ended photo-detection is disclosed. The methodology comprises: receiving an optical signal carried on an optical transmission medium and coherently detecting the received optical signal to produce a digitized signal; estimating a time-dependent random variable introducing distortion to the coherently detected signal; and subtracting the distortion from digitized signal to produce a distortion mitigated output signal.
Method And Apparatus For Generating 8-QAM-Modulated Optical Signal,
Tue Dec 13 16:06:45 EST 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,
Tue Dec 06 16:06:43 EST 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,
Tue Jul 19 16:05:46 EDT 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,
Tue Mar 29 16:04:45 EDT 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,
Tue Mar 01 16:04:33 EST 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,
Tue Aug 03 15:04:19 EDT 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,
Tue Jun 29 15:04:08 EDT 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,
Tue Jun 15 15:04:02 EDT 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,
Tue Mar 02 15:03:36 EST 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,
Tue Dec 22 16:08:00 EST 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,
Tue Jun 30 16:07:33 EDT 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,
Tue Jun 30 16:07:32 EDT 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,
Tue Dec 09 18:13:18 EST 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,
Tue Nov 04 18:13:07 EST 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,
Tue Oct 14 18:13:02 EDT 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,
Tue Mar 11 18:12:40 EDT 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,
Tue Oct 09 18:12:16 EDT 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,
Tue Oct 02 18:12:15 EDT 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,
Tue Nov 28 18:11:44 EST 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,
Tue May 16 18:11:12 EDT 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,
Tue Nov 02 18:10:08 EST 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.
