Optical Code Division Multiple Access (OCDMA) is a promising technology for efficiently sharing resource of future optical networks among multiple nodes while managing the unavoidable Multiple Beam Interference (MBI). MBI arises when multiple users share the optical channel concurrently using signature codes. In this work, we investigate the impact of MBI on OCDMA network based on State of Polarization (SOP) encoding. The signature codes rotate the beam SOP for each node attached to the optical network. The considered signature codes are the asynchronous Gold code set and the Synchronous Hadamard code set. It is well known that conventional CDMA systems provide significant processing gain improvement in terms of the required Signal to Noise Ratio SNR, to achieve a given Bit Error Rate (BER) performance for single node transmission. However, the performance deteriorates as more active concurrent nodes transmit on shared channel. Interestingly, we show that the BER performance improves as number of active nodes increases when synchronous Hadamard code set is used as the signature waveform. To the best of our knowledge, this is a novel behavior in OCDMA systems. For instance, it is found that, by using intensive numerical simulations, a Hadamard code set of length 32 chips at a fixed SNR of -4 dB, the BER drops from 10-2 for a single user scenario to 10-6 for 32 concurrent users, i.e., a four order of magnitude improvement in BER performance.