Abstract

Optical parametric amplifiers provide gain to an input signal in a phase-sensitive fashion, hence the name phase-sensitive amplifiers (PSAs). Recently, quantum-limited PSAs with large gains have been demonstrated [1]. PSAs possess many properties that make them attractive for use in ultra-high-speed optical communications and networks. In summary: PSAs do not add any spontaneous-emission noise; the signal-to-noise ratio is preserved as the signal is amplified. In this sense they make an ideal amplifier with 0 dB noise figure [1]. PSAs are unidirectional in that the gain exists only for light propagating in the same direction as the pump light in the amplifier. PSAs can be designed for operation at any wavelength; the full low-loss window of the fused-silica fiber thus becomes usable. In contrast, the erbiumfiber amplifier provides gain over a relatively narrow wavelength range (≃ 40 nm). In a fiber/amplifier line the use of PSAs automatically compensates for the degrading effects of dispersion; there is no need for extra dispersion-compensating devices [2]. Short pulses can propagate without significant broadening over distances that are up to 100 times longer than the dispersion length of the fiber. Moreover, dispersion can be compensated in both the positive and the negative group-velocity dispersion regions of the fused-silica fiber. The dispersion-compensation properties can be very useful for upgrading the capacity of the existing 1.3 μm fiber plant. When used with solitons, PSAs can reduce the Gordon-Haus timing jitter without the need for extra filters [3]. Solitons can propagate over long distances without generating dispersive radiation during their amplification and decay between the amplifiers [4].

© 1994 Optical Society of America