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An optical phase‐sensitive amplifier (PSA) has the potential of low‐noise optical amplification. A frequency non‐degenerate PSA (ND‐PSA) can amplify arbitrary modulation formats including higher‐order QAM. The ND‐PSA requires a co‐propagating phase conjugated light (idler light) that has been conventionally created with an optical phase conjugator at the transmitter side. We propose a transmitter configuration using simultaneous signal generation of both a signal and its idler by double‐sideband modulation for transmission systems with ND‐PSAs. The proposed scheme provides a simple configuration with a single Mach–Zehnder amplitude modulator without optically creating the idler light. We performed experiments using 16QAM, 32QAM, and probabilistically shaped 256QAM signals. As a result, a phase‐sensitive amplification with each modulation format was successfully demonstrated using the proposed transmitter configuration.

We achieved 16QAM signal amplification using a PPLN-based PSA with high gain linearity. Phase noise cancellation and an improved SNR were successfully demonstrated. The applicability of the amplification of multi-carrier signals and two orthogonally-polarized signals was also confirmed toward ultra-high spectrally efficient signal amplification.

A multiple quasi-phase matched IiNbO^sub 3^ device in a four-port fibre-pigtail module for variable difference frequency generation (DFG) is described. The module structure realises DFG pumped by second-harmonic light that results in wavelength conversion with low crosstalk. The module is also used to demonstrate polarisation-insensitive conversion. This device technology will be useful for future photonic networks that employ a grouped wavelength path.

A multiple quasi-phase matched IiNbO sub( 3) device in a four-port fibre-pigtail module for variable difference frequency generation (DFG) is described. The module structure realises DFG pumped by second-harmonic light that results in wavelength conversion with low crosstalk. The module is also used to demonstrate polarisation-insensitive conversion. This device technology will be useful for future photonic networks that employ a grouped wavelength path.

In this paper, a high-power 3.4 μm difference frequency generation (DFG), using a quasi-phase-matched Zn:LiNbO3 waveguide fabricated by direct bonding technology, is presented. The high resistance of the waveguide to photorefractive damage allows high-power generation. A 65 μW mid-infrared output was obtained using a continuous-wave high-power fibre amplifier as pump source. The DFG source can access over 10 nm continuously simply by scanning the signal wavelength, and will be useful for real-time trace gas sensing.