Masuo Suyama

Modulation and demodulation techniques in optical heterodyne PSK transmission systems

Modulation and demodulation techniques are described for an optical PSK heterodyne transmission system operating at 560 Mb/s and 1.2 Gb/s. Performance limitations affecting the receiver sensitivity in a 1.2-Gb/s DPSK system, such as laser phase noise, phase modulation depth, IF center frequency deviation, and local laser power, are studied. High receiver sensitivities for PSK systems were achieved. The applicability of the Mach-Zehnder modulator as a phase modulator for 1.2-Gb/s DPSK is also demonstrated. A 1.2-Gb/s DPSK transmission of over 100 km, using polarization diversity with novel polarization-insensitive automatic frequency control in an attempt to overcome signal fading caused by polarization fluctuation in the transmitting fiber, is also described. A receiver sensitivity of less than -42.8 dBm and varying within 1.4 dB for all states of polarization was achieved. A multichannel high-definition TV (HDTV) transmission experiment using a DPSK polarization-diversity tunable receiver is described. >

A 200 Mbit/s Synchronous TDM Loop Optical LAN Suitable for Multiservice Integration

This paper describes a 200 Mbit/s multiservice optical local area network (LAN) using a synchronous TDM loop structure. The LAN consists of a central supervisory node and multiple service nodes connected by an optical fiber loop. Each service node supports communication channels which have access to allocated time slots in TDM frames continuously circulating on the loop. Multiple independent communication paths of various speeds up to 140 Mbits/s and various modes including point-to-point, ring, and multicast, can be provided between the channels on the loop. The ring will be useful to support ring networks, such as a token ring. The structure of this LAN is quite suitable for integration of multiple services, including video, image, data, and voice, since each service can independently choose its own speed, access method, and mode. In this development, various LSI-based high-speed hardware technologies including compact E/O and O/E modules, GaAs 4 × 4 matrix switch LSIs, and high-speed TDM-processor LSIs, which are versatilely applicable to high-speed LANs ranging from 100 Mbits/s up to 560 Mbits/s, have been successfully introduced and compact LAN equipment has been obtained. This paper deals mainly with the system and hardware structure of this LAN, together with high-speed hardware technologies. An outline of firmware and network operation, and an application example are also described.

Four 5-Gbit/s WDM transmission over 4760-km straight-line using pre- and post-dispersion compensation and FWM cross talk reduction

Summary form only given. In conclusion, four 5.332-Gbit/s optical WDM signals were successfully transmitted over 4760-km straight-line using pre and post-compensation of group velocity dispersion (GVD) for each channel and the reduction of four wave mixing (FWM) cross talk with high-speed polarization scrambling.

Theoretical and experimental study of self-filtering effect in concatenated erbium-doped fiber amplifiers

This paper describes the self-filtering effect which appears in concatenated erbium-doped fiber amplifier (EDFA) systems. Employing a theoretical model we observed how the self-filtering wavelength is affected by the variation of some EDFA parameters, such as gain, fiber composition, pump wavelength and temperature. By a recirculating loop experiment which simulates a concatenated repeater transmission system, we measured the evolution of the amplified spontaneous emission (ASE) spectra with the number of circulations, and with the loss of the loop. We found a good agreement between the theoretical simulations and the experiments. >

Optical heterodyne image-rejection receiver for high-density optical frequency division multiplexing system

An optical heterodyne image-rejection receiver (IRR) for high-density optical frequency division multiplexing (OFDM) systems is described. The IRR was realized using balanced receivers, which showed more than 18-dB suppression over the 1.5-3.0-GHz IF region. Measured crosstalk penalties in a two-channel 560 Mb/s differential phase-shift keyed (DPSK) heterodyne optical communication system were realized for the first time. The crosstalk penalties in an OFDM system are estimated theoretically with and without the IRR. The required channel spacing and number of channels that can be accommodated in the 10-nm tuning range of the local laser are presented. A particular configuration of the IRR, its operation, and its performance limitations are discussed. The experimental results for image-rejection reception in a two-channel 560-Mb/s DPSK system are also given. Crosstalk penalties are estimated experimentally and compared to the theoretical calculation. Since the conventional configurations of the IRR are very sensitive to the polarization fluctuation of the transmitted signals, polarization-insensitive IRRs are proposed and their features are considered. >

1.05 Tbit/s WDM transmission over 8,186 km using distributed Raman amplifier repeaters

We have achieved a 1.05 Tera bit/s WDM transmission over 8186 km using distributed Raman amplifier repeaters. Signal bandwidth was 31.2 nm and the optical SNR improvement was about 1.5 dB in contrast to using an EDFA repeater.

2.4 Tbit/s WDM transmission over 7400 km using all Raman amplifier repeaters with 74 nm continuous single band

We have demonstrated 240 channel, 10 Gbit/s WDM transmission over 7404 km using all Raman amplifier repeaters with a continuous signal bandwidth of 74 nm and dispersion-managed fiber with our proposed dispersion map for transmission systems based on distributed Raman amplifiers (DRA).

128-Gbit/s WDM transmission of 24 5.3-Gbit/s RZ signals over 7828 km using gain equalization to compensate for asymmetry in EDFA gain characteristics

Erbium-doped fiber amplifiers (EDFAs) with broad signal bandwidth, low NF and high output power, and transmission characteristic improvement using chromatic dispersion management and modulation format are required for long-haul, wavelength-division multiplexing (WDM) transmission systems. We performed a 24 5.3-Gbit/s WDM transmission experiment over 7828 km using gain equalization to compensate for the asymmetry of the EDFA gain characteristics, RZ modulation format, and both pre- and post-compensation of chromatic dispersion.

Active Gain Slope Compensation in Large-Capacity, Long-Haul WDM Transmission System

Large-capacity, long-haul wavelength-division-multiplexing (WDM) transm1ss1on systems require broad WDM signal bandwidth, which can be expanded with broadband erbium-doped fiber amplifier (EDFA),1 gain-equalizer (GEQ),2,3 and pre-emphasis at the transmitter.

PDL-induced noise reduction in long-haul transmission systems using synchronous polarization scrambling

We proposed polarisation dependent loss (PDL) induced noise reduction method using a band-rejection-filter in a long-haul large-capacity WDM transmission system with synchronous polarization scrambling. We demonstrated the effect in an 8 channel 5.332 Gbit/s WDM transmission experiment using this method.