A demultiplexing scheme based on semiconductor optical amplifier (SOA) and optical filter for optical time division multiplexing differential quadrature phase shift keying (OTDM-DQPSK) system is proposed and investigated experimentally. With only a common half baudrate electrical clock modulated 33% duty cycle return-to-zero (RZ-33) optical clock signal as pump, this scheme is cost-effective, energy-efficient, and integration-potential. A proof-of-concept experiment is carried out for the demultiplexing of a 2 \times 40-GBd OTDM-DQPSK signal. Error-free performance is demonstrated, and the average power penalty for both channels is about 3 dB.