K.J. Park

Performance comparisons of chromatic dispersion-monitoring techniques using pilot tones

We report on the performance comparisons of the chromatic dispersion-monitoring techniques using pilot tones. The results show that the monitoring technique using phase-modulated pilot tones provides superior performances compared with the technique using amplitude-modulated pilot tones.

Optical performance monitoring techniques based on pilot tones for WDM network applications

Feature Issue on Optical Performance Monitoring (OPM). We report on the pilot-tone-based optical performance monitoring techniques for use in the wavelength-division multiplexing (WDM) network. We first described the operating principle of the pilot-tone-based monitoring technique and estimated its scalability by analyzing potential problems. We then reviewed the techniques proposed for monitoring various optical parameters of WDM signals--such as optical power, wavelength, optical path, and cross talk--using pilot tones. We also presented examples of various network elements using the pilot-tone-based monitoring technique. In addition, we reviewed the pilot-tone-based monitoring techniques used in adaptive compensators for chromatic dispersion and polarization-mode dispersion, and we discussed their limitations and possible solutions. For example, we demonstrated a simple technique for monitoring the chromatic dispersion and polarization-mode dispersion simultaneously, without their affecting each other, by scrambling the state of polarization of the optical signal.

A novel optical signal-to-noise ratio monitoring technique for WDM networks

We propose and demonstrate a novel optical signal-to-noise (OSNR) monitoring technique based on receiver noise analysis. The results show that the accuracy of the proposed technique is better than 1 dB when the OSNR was 16-28 dB.

Novel mode converter based on hollow optical fiber for Gigabit LAN communication

A novel mode converter based on a hollow optical fiber is proposed to reduce the differential modal delay penalty in optical transmission over multimode fibers (MMFs). The device adiabatically converts a fundamental mode in a single-mode fiber to a ring-shaped mode in order to excite selectively a set of higher order modes with a similar group velocity in MMF, maintaining center-launching configuration. The mode converter is composed of serially concatenated concentric segments of a single-mode, hollow, and multimode optical fiber. For 2.5-Gb/s transmission over 500-m-long MMF using a laser diode transmitter, the proposed mode converter shows improvement in bit-error-rate performance at both wavelengths of 1.31 and 1.55 /spl mu/m.

Effects of stimulated Raman scattering on pilot-tone-based WDM supervisory technique

We report on the effects of stimulated Raman scattering (SRS) on the pilot-tone-based wavelength-division-multiplexing (WDM) monitoring technique. The SRS-induced ghost tones were measured after compensating the effects of erbium-doped fiber amplifiers (EDFAs) slow gain dynamics. Using these results, we estimated the maximum size of WDM network that the pilot-tone based monitoring technique could support.

A cold-start WDM system using a synchronized etalon filter

We demonstrate a 4/spl times/2.5 Gb/s cold-start WDM system using a synchronized etalon filter. This system automatically operated its transmitter lasers at the standardized wavelengths of 1547.82+n/spl times/0.8 nm (193.686-n/spl times/0.100 THz), where n is the channel number, to an accuracy of 1 GHz, The output power of each laser was also adjusted to be 0/spl plusmn/0.1 dBm simultaneously. Error-free transmission (BER <10/sup -9/) was achieved within 20 s after turning on the systems power supply.

Chromatic dispersion monitoring technique in WDM network

We demonstrated a simple technique that can be used to monitor the chromatic dispersion accurately in WDM networks. This technique could monitor the chromatic dispersion of each channel with accuracy better than 60 ps/nm after 640-km transmission over nonzero dispersion shifted fibre (NZDSF). We believe that this technique could be used for the efficient chromatic dispersion compensation in WDM networks.

Optical channel monitoring technique using phase-modulated pilot tones

We report on the pilot-tone-based optical channel monitoring technique for use in wavelength-division-multiplexing (WDM) networks. The proposed technique can monitor the wavelengths of WDM signals using phase-modulated pilot tones. Unlike the previously proposed monitoring technique using amplitude-modulated pilot tones, the proposed technique does not suffer from the cross-gain modulation and stimulated Raman scattering. The results show that the proposed technique could not be deteriorated by the chromatic dispersion.

OSNR monitoring technique based on orthogonal delayed-homodyne method

We have proposed and demonstrated a simple technique to monitor the OSNR in WDM networks. This technique has no pattern dependency and could measure the receiver noise power within the modulation bandwidth by using the orthogonal delayed-homodyne method. The results show that the proposed technique could measure the OSNRs of WDM channels with accuracy better than 0.5 dB even after transmission over 640 km of single mode fibre.The authors propose and demonstrate a simple technique to monitor the optical signal-to-noise ratio (OSNR) of wavelength-division-multiplexing (WDM) signals using the orthogonal delayed-homodyne method. This technique estimates the OSNR by analyzing the receiver noise characteristics after eliminating the signal components at a specific frequency within the modulation bandwidth. The results show that the OSNR of WDM signals could be monitored with accuracy better than 0.5 dB in the range of 12/spl sim/35 dB.

Transmission of 2.5-Gb/s WDM channels spaced at 5 GHz over 480 km of single-mode fiber

We have demonstrated the transmission of six 2.5-Gb/s wavelength-division-multiplexed (WDM) signals spaced at 5 GHz over 480 km of single-mode fiber. In this experiment, the WDM signals were demultiplexed by using a simple optical filter despite their extremely narrow channel spacing. The optical bandwidth of this filter was optimized by considering both the interchannel crosstalk and intersymbol interference. The results indicate that it should be possible to transmit more than 1000 2.5-Gb/s channels spaced at 5 GHz.