NTT Research and Development 2012 Review of Activities

Overview

Future high-capacity photonic network systems will need higher SNRs^*1 because their capacity is limited by nonlinear impairments in optical fiber and noise from optical amplifiers. When amplifying optical signals, a deterioration in signal quality is unavoidable if conventional laser amplifiers such as EDFAs^*2 are used. NTT Laboratories demonstrated a phase sensitive amplifier (PSA) based on a PPLN^*3 waveguide device allowing for highly efficient nonlinear effects and achieved low noise amplification beyond the theoretical limit of conventional laser amplifiers. The PSA can theoretically have zero additional noise and is thus promising for the key technologies in future photonic networks.

Features

• Optical signals can be amplified without additional noise.
• A low noise figure of 2.2 dB, below the quantum limit (3 dB) of a laser amplifier, was experimentally confirmed.
• The PSA amplifies only the in-phase component and deamplifies the quadrature one.
• Deamplification of the quadrature phase component can reduce the phase noise of the optical signal.

Application scenarios

• Low-noise amplifiers in future high-speed, high-capacity photonic network systems
• Optical transmitters with chirp-reducing capability exploiting the phase squeezing property of the PSA.

• *1 SNR: Signal-to-Noise Ratio
• *2 EDFA: Erbium-Doped Fiber Amplifier
• *3 PPLN: Periodically Poled Lithium Niobate