Streaming media, mobile data traffic, and cloud computing are fueling the ever increasing demand for bandwidth. In order to meet this demand, the fiber optic communications industry is moving towards coherent modulation formats to increase capacity. Compared to conventional on-off keying modulation formats, coherent formats encode information in both phase and amplitude of a signal. Photonic integrated circuits have the potential to lower the cost of that comes with more complex transmitter and receiver components. Three different photonic integrated circuit technologies will be presented: a differential quadrature phase- shift-keying (DQPSK) receiver on the hybrid silicon platform, a coherent dual- quadrature receiver on InP with an integrated widely-tunable local oscillator, and a differential phase-shift-keying (DPSK) wavelength converter, also on InP. The wavelength converter has regenerative properties stemming from its the nonlinear transfer function, and has the potential to become a lower power alternative to a coherent tranceiver.