Phase-sensitive amplification using gain saturation in a nonlinear Sagnac interferometer

Abstract

Phase-sensitive amplification of picosecond optical pulses was demonstrated using an SOA as the nonlinear medium inside a Sagnac interferometer. Ratios of maximum to minimum gain of more than 3:1 were experimentally measured. Numerical simulations using a semiconductor amplifier model are consistent with experiments.

Phase discrimination and simultaneous frequency conversion of the orthogonal components of an optical signal by four-wave mixing in an SOA

“…As with coherent detection, phase locking is required, in this case between the signal and the pump comb. The nonlinear optical mixing elements used in this work were semiconductor optical amplifiers (SOAs), which are rarely employed in phase-sensitive applications [8], but it is likely that other nonlinear devices could produce similar results. The use of SOAs here provided overall signal gain and sufficient contrast for phase sensitive signal processing while requiring only sub-milliwatt input powers and avoiding problems caused by stimulated Brillouin scattering (SBS).…”

“…In an alternative arrangement (Fig. 1b), a pair of nonlinear devices is placed in the arms of a symmetrical Mach-Zehnder interferometer (MZI), which is equivalent to the use of a Sagnac interferometer in the single-pump degenerate PSA [7,8]. The advantage is that the two output signals and other modulation products generated at even multiples of ∆f appear at one output port, while the products at odd multiples of ∆f, including the amplified pumps, appear at the other.…”

“…With either arrangement, the mixing products generated at the signal frequency only add constructively and enhance the signal when the signal and the pumps have the correct phase relationship. In general, phase selectivity requires the signal to beat with more than one pump (unless the pump and signal share the same frequency [7,8]). Frequency conversion using four-wave mixing can also be made phase sensitive if multiple pumps are employed [9].…”

A novel scheme of cascaded four-wave mixing for phase-sensitive amplification in nonlinear optical fibre

“…PSAs have been demonstrated in materials with second-order nonlinearity in periodically poled Lithium Niobate and with third-order nonlinearity in a highly nonlinear fibre (HNLF), semiconductor optical amplifiers and silicon and chalcogenide waveguide (2,3,(12)(13)(14)(15)(16). Among these media, realization of PSA in HNLF is notably interesting for practical network applications due to its low loss, long interaction length for nonlinear amplification, highpower efficiency and ease of system integration (6,7,(17)(18)(19). Two techniques of PSA based on HNLF have been demonstrated: nonlinear optical loop mirror (NOLM) and phase-sensitive fibre optical parametric amplifier (FOPA) (4,9,(17)(18)(19)(20).…”

“…Among these media, realization of PSA in HNLF is notably interesting for practical network applications due to its low loss, long interaction length for nonlinear amplification, highpower efficiency and ease of system integration (6,7,(17)(18)(19). Two techniques of PSA based on HNLF have been demonstrated: nonlinear optical loop mirror (NOLM) and phase-sensitive fibre optical parametric amplifier (FOPA) (4,9,(17)(18)(19)(20). In NOLM based PSA, signal and pump (optical reference at signal frequency) waves are used at same frequency, leading to degradation in signal quality due to guided acoustic-wave Brillouin scattering of pump waves (20,21).…”