We describe phase-diversity optical coherent receivers (CRx) using the phase-shifting-interference (PSI) framework. The goals of the analysis are several-fold. First, we show that coherent detection can be realized with optical hybrids that have an arbitrary number of branches and phase shifts using a closed-form solution of the inphase-quadrature mapping. Second, we show that CRx with 2×4 90° hybrids using balanced detection (BD) and CRx with 2×3 120° hybrid using single-ended detection (SED) perform optimally compared to alternative configurations. A proof-of-concept WDM colorless 10×132-Gb/s PDM-QPSK transmission experiment is conducted. We demonstrate that an example of arbitrary phase diversity CRx with a 2×3 90° hybrid SED operates with a 0.3dB signal-to-noise-ratio (SNR) penalty relative to conventional CRx at 6400km and 4480km for bit-error-rates below the threshold of 2×10−2 and the threshold of 3.8×10−3 respectively. The sensitivity degradation of the 2×3 90° hybrid SED with respect to the 2×4 90° hybrid BD in the shot noise limited regime at a distance of 4480km is 3dB, which matches well with the predicted penalty from the PSI analytical model. To the best of our knowledge, this paper is the first attempt to model a CRx using the PSI model.