Phase-sensitive amplifiers for nonlinearity impairment mitigation in optical fiber transmission links
Doctoral thesis, 2021

The fundamental limitations in fiber-optic communication are caused by optical amplifier noise and the nonlinear response of the optical fibers. The quantum-limited noise figure of erbium-doped fiber amplifiers (EDFAs) or any phase-insensitive amplifier is 3 dB. However, the noise added by the amplification can be reduced using phase-sensitive amplifiers (PSAs), whose quantum-limited noise figure is 0 dB. PSAs can also compensate for the nonlinear distortions from the optical transmission fiber in the copier-PSA implementation. At the transmitter, a copier which is nothing but a phase-insensitive amplifier, is used to create a conjugated copy of the signal. The signal and idler are then copropagated in the fiber link, experiencing correlated nonlinear distortions. The nonlinear distortions are reduced by the all-optical coherent superposition of the signal and idler in the PSA.

In this work, an investigation is made for the nonlinearity mitigation using the PSAs, by calculating the residual nonlinear distortion after the coherent superposition in a copier-PSA link. The nonlinearity mitigation efficiency in PSA links is studied with respect to modulation formats, symbol rates and number of wavelength channels. The effectiveness of nonlinearity mitigation is found to increase with higher-order modulation formats. However, the efficiency of nonlinearity mitigation decreases with increasing number of wavelength channels and increasing symbol rate resulting in larger residual nonlinear distortions. A modified Volterra nonlinear equalizer (VNLE) is implemented to reduce the residual nonlinear distortions after PSAs in single- and multi-channel PSA links. Cross-phase modulation mitigation using PSAs is also demonstrated.

Volterra nonlinear equalizer

nonlinearity mitigation

self-phase modulation mitigation

low-noise amplification

phase-sensitive amplifier

modulation formats

cross-phase modulation mitigation


optical transmission

Opponent: Professor Michael Vasilyev, University of Texas, USA


Kovendhan Vijayan

Chalmers, Microtechnology and Nanoscience (MC2), Photonics

Analysis of nonlinearity mitigation using phase-sensitive optical parametric amplifiers

Optics Express,; Vol. 27(2019)p. 31926-31941

Journal article

Optical Bandwidth Dependency of Nonlinearity Mitigation in Phase-Sensitive Amplifier Links

European Conference on Optical Communication, ECOC,; Vol. 2018-September(2018)

Paper in proceeding

Long-haul transmission of WDM signals with in-line phase-sensitive amplifiers

IET Conference Publications,; Vol. 2019(2019)

Paper in proceeding

Cross-phase modulation mitigation in phase-sensitive amplifier links

IEEE Photonics Technology Letters,; Vol. 31(2019)p. 1733-1736

Journal article

K VIJAYAN, Z HE, B FOO, J SCHRÖDER, M KARLSSON ,P A ANDREKSON, "Phase-sensitively amplified wavelength-division multiplexed optical transmission systems"

The amount of information that can be sent through an optical fiber is basically limited by noise added by optical amplifiers. Another main limitation comes from the nonlinear distortions caused by the optical fiber at higher intensities of light. There is a special kind of amplifier that is capable of amplifying the signal by adding less noise compared to the conventional amplifiers known as phase-sensitive amplifiers (PSAs). PSAs can also minimize the nonlinear distortions caused by the optical fiber. In this thesis, we analyze how PSAs can reduce the nonlinear distortions and verify it with numerical simulations and experiments.

Areas of Advance

Information and Communication Technology


C3SE (Chalmers Centre for Computational Science and Engineering)

Subject Categories

Electrical Engineering, Electronic Engineering, Information Engineering



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4948





Opponent: Professor Michael Vasilyev, University of Texas, USA

More information

Latest update

5/6/2021 3