Toward noiseless amplification for optical communication: Utilizing phase-sensitive amplification based on frequency non-degenerate four-wave-mixing in optical fiber

Fiber optical parametric amplifiers (FOPAs) amplify an input signal based on the four-wave-mixing (FWNI) process in fiber. Similar to erbium doped fiber amplifiers and Raman amplifiers, FOPAs can amplify an input signal regardless of its optical phase. When used this way it is referred to as a phase-insensitive amplifier (PIA). FOPAs can also amplify an input signal in which the gain of the amplification depends on the input signal's optical phase. When used this way it is referred to as a phase-sensitive amplifier (PSA). Fiber PSAs amplify the signal component that is in phase with the pump while attenuate the quadrature component. PSAs offer better noise performance than PIAs do.; In 1.5 mum telecom band fiber PSAs demonstrated so far are majorally based on the frequency degenerate FWM with Sagnac interferometer configuration. The pump and signal are of the same optical frequency. Among the drawbacks frequency degenerate PSA has, two are significant. First, the amplified signal suffers the thermal noise induced by the guided acoustic wave Brillouin scattering (GAWBS) effect. Secondly, it cannot provide amplification for wavelength division multiplexed (WDM) signals due to its frequency nature. However, these drawbacks could be overcome when the frequency non-degenerate PSAs are introduced. The pump-signal optical frequency separation is readily achieved to be much larger than the bandwidth of the GAWBS effect. Also, multiple channels of signals could obtain simultaneous phase-sensitive amplification from the frequency non-degenerate PSAs as long as the phase relationship is set right for each channel.; In this work the first frequency non-degenerate fiber PSA in telecom band is demonstrated, achieving error-free operation with a dispersion compensated 60km-long single-mode fiber (SMF) transmission. Simultaneous phase-sensitive amplification of three channels of continuous wave lights is also accomplished. Besides a phase self-stabilized PIA-SMF-PSA configuration allows for the first observation of stable phase-sensitive amplification and de-amplification. This series of fiber PSA experiments demonstrate the feasibility of the in-line fiber phase-sensitive amplification based on the frequency non-degenerate FWM process. These works will lead to further investigation of in-line phase-sensitive amplification of multichannel signals, a possible solution to upgrade optical communication.