• The Journal of the Korea institute of electronic communication sciences
• /
• v.8 no.9
• /
• pp.1343-1349
• /
• 2013

In optical fiber communications, several newly-developed signal formats are used to obtain the best performance within limited spectral bandwidth. CSRZ (carrier-suppressed return-to-zero) format is one of the new signal formats, which has better spectral efficiency and better robustness to dispersion than RZ (return-to-zero) format. Thus it is widely used for demonstrating high-speed optical communication systems. In an earlier research, we proposed a clock-extraction method of CSRZ signal to monitor chromatic dispersion. However, the clock-frequency component extracted by the clock-extraction method can be affected by the bandwidth of a transmitter or a receiver. Therefore, in this paper, we investigate the effect of bandwidth on the chromatic dispersion monitoring of CSRZ signal based on clock-frequency component. As a result, we propose a couple of robust clock-extraction methods to monitor chromatic dispersion in CSRZ signal.

• ETRI Journal
• /
• v.30 no.3
• /
• pp.461-468
• /
• 2008

This paper presents a chromatic dispersion monitoring technique using a clock-frequency component for carrier-suppressed return-to-zero (CSRZ) signal. The clock-frequency component is extracted by a clock-extraction (CE) process. To discover which CE methods are most efficient for dispersion monitoring, we evaluate the monitoring performance of each extracted clock signal. We also evaluate the monitoring ability to detect the optimum amount of dispersion compensation when optical nonlinearity exists, since it is more important in nonlinear transmission systems. We demonstrate efficient CE methods of CSRZ signal to monitor chromatic dispersion for optimum compensation in high-speed optical communication systems.

• ETRI Journal
• /
• v.30 no.2
• /
• pp.249-254
• /
• 2008

In this paper, we demonstrate an electrically band-limited carrier-suppressed return-to-zero (EB-CSRZ) signal generator operating up to a 10 Gbps data rate comprising a single-stage Mach-Zehnder modulator and a wideband signal mixer. The wideband signal mixer comprises inverter stages, a mixing stage, and a gain amplifier. It is implemented by using a 0.13 ${\mu}m$ CMOS technology. Its transmission response shows a frequency range from DC to 6.4 GHz, and the isolation response between data and clock signals is about 21 dB at 6.4 GHz. Experimental results show optical spectral narrowing due to incorporating an electrical band-limiting filter and some waveform distortion due to bandwidth limitation by the filter. At 10 Gbps transmission, the chromatic dispersion tolerance of the EB-CSRZ signal is better than that of NRZ-modulated signal in single-mode fiber.