The noise model of temporal phase optical code-division multiple access (OCDMA) system is given. The concept of self beat noise induced by inter symbol interference(ISI) is proposed. The impact of multiple access interference(MAI), ISI and self beat noise on system performance is analyzed by using saddle-point approximation and the bit error rate(BER) expression of the system is presented. Simulations on the systems with optimal threshold and optical hard limiter show that the error probability of symbol “1” is the key factor to the system performance and it is also the main matter for on/off keying(OOK) system to overcome. A balance detection system with two en/decoders is presented and its performance is analyzed and compared with traditional OOK system. Results show its superior performance to the traditional one.