To be used for optical coherent detection such as DP-QPSK receivers, Optoplex’s ten-port 2x8 Coherent Mixer (aka QPSK mixer) combines the incoming signal with a local oscillator to generate eight light states in the complex-field space. The eight light output signals can then be coupled into four pairs of balanced detectors. The block diagram below shows the application of a 2x8 coherent mixer in a DP-QPSK receiver. Since the mixing process is data rate independent, the devices can be used for any data rate in applications such as 40Gb/s or 100Gb/s transmission systems.
Optoplex’s 2x8 Coherent Mixer is free-space micro-optics-based and patent pending. The device exhibits highly athermal behavior in terms of insertion loss and phase error. When the output signals are detected by four pairs of balanced receivers, both the amplitudes and the relative phase information of the input signal can be extracted for signal amplification and cost-effective compensation of optical transmission impairments, such as dispersion and PMD, in the electronic domain.
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