Optical DPSK demodulator

An optical DPSK demodulator is a device that provides a method for converting an optical differential phase-shift keying (DPSK) signal to an intensity-keyed signal at the receiving end in fiber-optic communication networks.

It is also known as delay line interferometer (DLI), or simply called DPSK demodulator.

The DPSK decoding method is achieved by comparing the phase of two sequential bits.

An incoming DPSK optical signal is first split into two beams with equal intensities, in which one beam is delayed in space by an optical path difference that introduces a time delay corresponding to one bit.

As a result, DQPSK allows processing of 40 Gbit/s data-rate in a 50 GHz channel spacing system.

Working principle of optical DPSK demodulation: (a) Incoming DPSK signal with uniform intensity, (b) 1-bit delay of the incoming DPSK signal with uniform intensity, and (c) Demodulated intensity signal after interference between ( a )/( a ′) and ( b )/( b ′).