A very simple integrated coherent receiver with record high sensitivity

Coherent WDM communication systems have a great potential to be applied to local broadband access networks due to their high sensitivity and densely spaced multichannel characteristics. Unfortunately, compared with a high-bit-rate direct detection system the installation cost of such a system is relatively high. Although the hybrid coherent system can reach almost shot noise limited sensitivity, the higher cost can prevent it from gaining ground in the long run. In this work, we report a high sensitivity integrated coherent receiver with very simple device structure. The fabrication process of this device is so simple that it involves virtually no more than making a distributed-Bragg-reflector (DBR) laser. The device structure and its possible application as a broadband access terminal device with both receiving and transmitting functions are shown. The device is composed of a tunable DBR laser and an integrated detector. The incoming ASK or FSK signals are mixed in the DBR local oscillator (LO) cavity.