NTT Research and Development 2009 Review of Activities

Overview

DQPSK^*1 modulation offers advantages in terms of high spectral efficiency and good dispersion tolerance, so it is utilized for transmission at more than 40 Gbit/s. An optical front-end^*2 for DQPSK signals consists of two delay-line interferometers (DLIs) and two balanced receivers. We have developed a very compact optical front-end with very compact novel design DLIs and a one-package two-channel balanced receiver. The compact front end is expected to help to miniaturize a 40-Gbit/s optical receiver.

Features

• DLIs based on a silica-based PLC^*3 provide high reliability and good producibility
• Very compact DLIs with a single-chip design
• Reduced power consumption of temperature control by half
• Single-package two-channel differential optical receiver with novel-design PDs and dual-channel one-chip high-speed amplifier IC
• High-speed feed-through^*4 signal output suitable for high-density board assembly

Application scenarios

• Optical receiver for 40-Gbit/s DQPSK communication with reduced module size and power consumption

• *1 DQPSK: Differential Quadrature Phase-Shift Keying (A digital modulation scheme that detects a 4-valued carrier-signal phase by comparing it with the phase of one-symbol-delayed part)
• *2 optical front end: An optical-signal-to-electrical-signal converter with DQPSK.
• *3 PLC: Planar Lightwave Circuit (An optical waveguide fabricated on a substrate and utilized in a wide variety of compact optical filters)
• *4 feed-through: A pin-formed interface that provides a more compact assembly than possible with a connector-type interface.