Relative intensity noise transfer in higher-order distributed amplification through ultra-long fiber cavities

Among the different possible amplification solutions offered by Raman scattering in optical fibers, ultra-long Raman lasers are particularly promising as they can provide quasi-losless second order amplification with reduced complexity, displaying excellent potential in the design of low-noise long-distance communication systems. Still, some of their advantages can be partially offset by the transfer of relative intensity noise from the pump sources and cavity-generated Stokes to the transmitted signal. In this paper we study the effect of ultra-long cavity design (length, pumping, grating reflectivity) on the transfer of RIN to the signal, demonstrating how the impact of noise can be greatly reduced by carefully choosing appropriate cavity parameters depending on the intended application of the system

RIN transfer in random distributed feedback fiber lasers

We numerically investigate relative intensity-noise transfer from a noisy pump to the generated Stokes component in random distributed feedback ultralong Raman fiber lasers. Results show transfer levels comparable to those in distributed Raman amplification and cavity-based ultralong Raman fiber lasers, but with some unique spectral features. © 2012 OSAThe authors wish to thank the financial support of Ministerio de Economía y competividad (MINECO) through grant TEC2011-27314.Peer Reviewe

Theory of fiber optic Raman polarizers

We propose and apply a theoretical description of a Raman amplifier based on the vector model of randomly birefringent fibers to the characterization of Raman polarizers. The Raman polarizer is a special type of Raman amplifier with the property of producing a highly repolarized beam when fed by relatively weak and unpolarized light. © 2010 Optical Society of America.This work was carried out in the framework of the Scientific Research Project of Relevant National Interest (PRIN 2008) titled “Nonlinear cross-polarization interactions in photonic devices and systems” (POLARIZON) and in the framework of the 2009 Italy–Spain Integrated Action “Nonlinear Optical Systems and Devices” (HI2008-0075).Peer Reviewe

Signal power asymmetry optimisation for optical phase conjugation using Raman amplification

We numerically optimise in-span signal power asymmetry in different advanced Raman amplification schemes, achieving a 3% asymmetry over 62 km SMF using random DFB Raman laser amplifier. We then evaluate the impact of such asymmetry on the performance of systems using mid-link OPC by simulating transmission of 7 x 15 Gbaud 16QAM Nyquist-spaced WDM-PDM signals. (C) 2015 Optical Society of Americ

Characterisation of random DFB Raman laser amplifier for WDM transmission

We perform a full numerical characterisation of half-open cavity random DFB Raman fibre laser amplifier schemes for WDM transmission in terms of signal power variation, noise and nonlinear impairments, showcasing the excellent potential of this scheme to provide amplification for DWDM transmission with very low gain variation

Signal power asymmetry optimisation for optical phase conjugation using random DFB laser Raman amplification

3 pags., 3 figs. -- Asia Communications and Photonics Conference, Hong Kong Hong Kong 19–23 November 2015 .-- OCIS codes: 060.2320, 060.1660We numerically optimise in-span signal power asymmetry in advanced Raman amplification schemes, reaching 3% over 62 km SMF, and evaluate its impact on the performance of systems using mid-link OPC using 7×15 16QAM Nyquist-spaced WDM-PDM.We acknowledge the support of the EU through the MSC IF ”CHAOS” and FP7 ITN programme ICONE, Spanish MICINN Grant RAMAS, TEC2011-27314 and UK EPSRC Programme Grant UNLOC EP/J017582/1.Peer reviewe

Optimal span length in high-speed transmission systems with hybrid Raman-erbium-doped fiber amplification

We show, using nonlinearity management, that the optimal performance in high-bit-rate dispersion-managed fiber systems with hybrid amplification is achieved for a specific amplifier spacing that is different from the asymptotically vanishing length corresponding to ideally distributed amplification [Opt. Lett. 15, 1064 (1990)]. In particular, we prove the existence of a nontrivial optimal span length for 40-Gbit/s wavelength-division transmission systems with Raman-erbium-doped fiber amplification. Optimal amplifier lengths are obtained for several dispersion maps based on commonly used transmission fibers. © 2005 Optical Society of America

Nonlinear inverse synthesis for optical links with distributed Raman amplification

Nonlinear Fourier transform (NFT) and eigenvalue communication with the use of nonlinear signal spectrum (both discrete and continuous) have been recently discussed as a promising transmission method to combat fiber nonlinearity impairments. However, because the NFT-based transmission method employs the integrability property of the lossless nonlinear Schrödinger equation (NLSE), the original approach can only be applied directly to optical links with ideal distributed Raman amplification. In this paper, we investigate in details the impact of a non-ideal Raman gain profile on the performance of the nonlinear inverse synthesis (NIS) scheme, in which the transmitted information is encoded directly onto the continuous part of the nonlinear signal spectrum. We propose the lossless path-averaged (LPA) model for fiber links with non-ideal Raman gain profile by taking into account the average effect of the Raman gain. We show that the NIS scheme employing the LPA model can offer a performance gain of 3 dB regardless of the Raman gain profiles

Performance optimization in ultra-long Raman laser amplified 10x30 GBaud DP-QPSK transmission:Balancing RIN and ASE noise

We experimentally evaluate the influence of RIN transfer from pump to signal on the transmission performance of a 10 × 30 Gbaud DP-QPSK transmission system using a 2nd-order ultra-long Raman fiber laser amplifier, considering the effect of cavity front-end reflectivity and forward pump power ratio. The evolution of the Q-factors with distance up to maximum reach is monitored for a 10 × 30 Gbaud DP-QPSK transmission system with WDM channels between 1542.94 nm to 1550.12 nm. A maximum transmission distance of 6479 km is found for configurations with low forward pump powers corresponding to the optimal balance between RIN and ASE impairments

Asymmetry Optimization for 10 THz OPC Transmission over the C + L Bands Using Distributed Raman Amplification

An optimized design for a broadband Raman optical amplifier in standard single-mode fiber covering the C and L bands is presented, to be used in combination with wideband optical phase conjugation (OPC) nonlinearity compensation. The use of two Raman pumps and fiber Bragg grating reflectors at different wavelengths for the transmitted (C band) and conjugated (L band) WDM channels is proposed to extend bandwidth beyond the limits imposed by single-wavelength pumping, for a total 10 THz. Optimization of pump and reflector wavelength, as well as pump powers, allows us to achieve low asymmetry across the whole transmission band for optimal nonlinearity compensation. System performance is simulated to estimate OSNR, gain flatness and nonlinear Kerr distortion