We report a silicon DQPSK receiver whose symbol rate can be varied by a tunable one-bit delay line including an all-pass micro-ring slow-light device. It also consists of Si-wire waveguides with spot-size converters, optimized splitters/couplers, heater-controlled Mach-Zehnder attenuators and phase shifters, 90° hybrid with a low-loss crossing and balanced Ge photodiodes, all of which are fabricated by using CMOS-compatible process. Demodulation was confirmed at symbol-rates of 7.4 - 9.0 Gbaud, corresponding to bit-rates of 14.8 - 18.0 Gb/s.