Optical networks-on-chip (ONoCs) represent an emerging technology for use as a communication platform for systems-on-chip (SoC). It is a novel on-chip communication system where information is transmitted in the form of light, as opposed to the conventional electrical network-on-chip (ENoC). This work studies the performance of a class of ONoCs that employ a single central passive-type optical router using wavelength division multiplexing (WDM) as a routing mechanism. The ONoC performance analysis has been carried out both at system-level (network latency and throughput) and at the physical level. In physical-level (optical) performance analysis of the ONoC, we study the communication reliability of the ONoC formulated by the signal-to-noise ratio (SNR) and the bit error rate (BER). Optical performance of the ONoC is carried out based on the system parameters, component characteristics and technology. The system-level analysis is carried out through simulation using flit-level-accurate SystemC model. Experimental results prove the scalability of the ONoC and demonstrate that the ONoC is able to deliver a comparable bandwidth or even better (in large network sizes) to the ENoC.