Phase-Sensitive Amplification in Optical Fibers

Abstract

We describe the progress in fiber-based phase-sensitive parametric amplifiers in both frequency-degenerate and frequency-nondegenerate configurations. We discuss their applications for phase regeneration, as well as for lumped and distributed noiseless amplification. 2005 Optical Society of America OCIS codes: (060.2320) Fiber optics amplifiers and oscillators; (190.4410) Nonlinear optics, parametric processes Phase-sensitive amplifiers (PSAs) have unique properties that allow them to break the 3-dB quantum limit of the optical amplifier noise figure [1], as well as provide the phase regeneration leading to suppression of frequency and timing jitters in optical transmission lines [2,3]. The first experimental demonstrations of sub-3-dB noise-figure (NF) PSAs were done in (2) -based devices [4,5]. The free-space bulk-crystal PSA also enabled noiseless amplification of images [6]. PSA's use in optical communication context, however, requires fiber-based approaches. One of such designs, based on a nonlinear optical loop mirror (NOLM), was introduced in [7] and successfully utilized in [8] for soliton regeneration in a long-term storage buffer. The solutions to synchronization of the pump and incoming signal phases were developed via pump injection locking [9] and optical phase-locked loop [10].Achieving the sub-3-dB NF in fiber-based PSAs, however, is challenged by the Guided Acoustic-Wave Brillouin Scattering (GAWBS) that introduces uncorrelated phase fluctuations in the counter-propagating NOLM arms, resulting in amplitude noise at the PSA output. The nearly noiseless PSA performance has nevertheless been experimentally demonstrated in [11,12], using pulses with orthogonal polarizations to cancel common GAWBS noise, followed by [13], where the GAWBS was avoided by conducting the NF measurements well above this noise's cut-off of ~2 GHz. Despite these successes, the complexity of GAWBS mitigation clearly limits the potential use of the NOLM-based PSAs. Even more importantly, the NOLM-based PSAs are inherently single-channel devices not compatible with modern wavelength-division-multiplexed (WDM) transmission systems.The above two drawbacks can be overcome in the new-generation fiber PSAs that are based on non-degenerate four-wave mixing (FWM) in fiber. By exciting a combination of the signal and idler waves at the input, such an optical parametric amplifier can be put into a phase-sensitive regime. Moreover, two independent modes involving signal-idler-wave combinations can be phase-sensitively amplified at the same time, resulting in the same bandwidth utilization as that of the frequency-degenerate PSA. Since all involved waves propagate in the same direction, the GAWBS perturbs all of them equally, with no impact on the PSA gain and noise. In addition, by using the widebandwidth parametric amplifiers (e.g. those involving two pumps [14]), one can simultaneously amplify many WDM channels, provided that their phases are synchronized up to a multiple of . In-depth analysis of NF of these devices indicates their po...

Noise performance of optical fiber transmission links that use non-degenerate cascaded phase-sensitive amplifiers

“…As is well known, phase-sensitive amplifiers (PSAs) have the potential to realize noiseless amplification [1], which is a highly attractive characteristic for high-sensitivity photodetection [2] as well as high-speed optical communications [3]. To date, most PSA experiments have been based on parametric processes in nonlinear crystals [4] or optical fibers [5].…”

“…Degenerate PSAs are more straightforward to realize [6,7], however, the inherent single-channel property limits their potential applications. For example, non-degenerate PSA schemes can realize exponential gain [3] and multi-channel amplification [8] without suffering the guided acoustic-wave Brillouin scattering, which makes them more promising in practical WDM systems, though rigorous phase-and frequency-locking among the pump, signal and idler waves is required.…”

Pump-degenerate phase-sensitive amplification in chalcogenide waveguides

“…This implementation of PSA can achieve high gain since the maximum phase-sensitive gain grows exponentially with pump power in the lossless case [12]. This type of PSA is also compatible with WDM operation [13,14]. However, twice the bandwidth of signal-degenerate PSA is required, unless an advanced modulation and detection method is used.…”

“…Despite significant progress in fundamental understanding and design of PSA systems, most demonstrations still rely on large-scale χ 3 materials, e.g., hundreds meters of highly nonlinear fiber (HNLF) [10][11][12][13][14][16][17][18] or meters of customized HNLF [19]. These meter-scale devices are not integrable, and few works have involved centimeter-long χ 2 devices [3].…”