High-bandwidth balanced photoreceiver suitable for 40-Gb/s RZ-DPSK modulation formats

A novel fully packaged balanced photoreceiver designed for 40-Gb/s differential phase shift keying (DPSK) applications at 1.55-mum wavelength is presented. Based on InP: Fe substrate, two waveguide-integrated photodiodes with spot size converters are monolithically integrated with a distributed amplifier. This configuration leads to a high symmetry of the two optical inputs and avoids interconnection parasitics. The RF output of the photoreceiver is dc-coupled, but the design enables an interfacing to subsequent electronics without external bias-tee by using a negative bias supply at the source terminal of the integrated amplifier. A reduction of system costs and required space will be obtained by this concept. Mounted in a butterfly package, a 3-dB cutoff frequency of 42 GHz is achieved. Return-to-zero (RZ)-DPSK experiments exhibit excellent operation of the balanced photoreceiver over a large dynamic range of optical input power up to +10 dBm. The high-power capability and the clear eye opening at low input power demonstrates the suitability for high performance core and metro systems.