Ultrafast Measurement of Optical DPSK Signals Using 1-Symbol Delayed Dual-Channel Linear Optical Sampling

• Published in: IEEE photonics technology letters Vol. 20; no. 11; pp. 948 - 950
• Main Authors: Okamoto, K., Ito, F.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.06.2008; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Constellation diagram; Delay; Delay lines; Differential phase shift keying; differential phase-shift keying (DPSK); Differential quadrature phase shift keying; Interferometers; linear optical sampling; Optical communication; Optical data processing; Optical interferometry; Optical noise; Phase measurement; phase noise; Photonics; Pulse measurements; Sampling; Sampling methods; Short pulses; Signal sampling; Symbols; Ultrafast optics
• ISSN: 1041-1135; 1941-0174
• DOI: 10.1109/LPT.2008.922334

We propose and demonstrate a 1-symbol delayed dual-channel linear optical sampling for observing optical differential phase-shift keying (DPSK) signals. As this technique is based on optical gate processing by means of interference with local short pulses, its performance allows ultrafast measurement for a symbol rate of greater than 100 Gsymbol/s. Moreover, as the new measurement apparatus employs a two-series interferometer system with a 1-symbol delay, the measured phase distribution reflects the signal quality between adjacent symbols of the optical DPSK signals. In our experiment, we successfully observe the waveform degradation caused by the coherence of the light source and the pattern effect of the phase modulator. The measurement system noise is also discussed.