107–112 Gbit/s fully integrated CDR/1:2 DEMUX using InP-based DHBTs

This paper presents a monolithically integrated clock and data recovery (CDR) circuit with 1:2 demultiplexer (DEMUX), which is capable of processing signals with data rates between 107 Gbit/s and 112 Gbit/s. The fabrication of the integrated circuit (IC) relies on an in-house InP double heterostructure bipolar transistor technology (DHBT) featuring cut-off frequency values of more than 350 GHz for both fT and fmax. The CDR concept is based on a half-rate circuit architecture, whose main components are a linear phase detector including a 1:2 DEMUX, a voltage controlled oscillator (VCO), and a loop filter. Mounted into a module, the CDR/1:2 DEMUX features proper operation at data rates up to 112 Gbit/s, whereas the recovered and demultiplexed data exhibit clear eye opening and a voltage swing of 500 mVpp. The half-rate clock signal extracted from the input data features a voltage swing of 250 mVpp. By using the CDR module in an optical system environment, a bit error rate (BER) well below 10⁻¹⁰ is obtained at 112 Gbit/s with a data word length ranging up to 2³¹–1.