T. Kawazawa

Field demonstration of endless polarization control in 195-km installed optical fiber submarine cable at a sea depth of 2900 m

A low-insertion loss module with rotatable fractional wave plates was used to achieve endless polarization control at the output of a 195-km-long 2900-m deep-sea optical fiber submarine cable. The module could be compensated for state of polarization (SOP) fluctuations for frequencies up to 3 Hz. It was confirmed that a module with mechanical rotatable fractional wave plates could be used to control the real polarization variations that occur in installed optical submarine cables.<<ETX>>

Effect of span loss increase on the optically amplified communication system

In optical fiber communication systems using Er/sup 3+/ doped fiber amplifiers operating in their compression region, the optical signal power is known to be restored by the self-healing effect in the case of the span loss increase. In this paper, the influence of such excess loss on the system transmission performance is experimentally and numerically investigated from the point of view of the system signal-to-noise ratio and Q-factor. The results show that the system SNR is not completely recovered although the signal power is restored after several stages of amplifiers and that there exists the residual degradation of the system SNR. Through a 5.3 Gb/s data transmission experiment over 3000 km, the transmission penalty due to the excess span loss is confirmed to be decided by this residual degradation of the system SNR. The obtained results can be used for system design and a plan of maintenance for the optical amplifier communication system.

Incident polarization angle and temperature dependence of polarization and spectral response characteristics in optical fiber couplers

The incident polarization angle and temperature dependence of the polarization and spectral response characteristics of three different types of fiber coupler are presented. The couplers are (1) the biconicalfused- twisted-taper single-mode fiber (coupler A), (2) the asymmetric-etched-fused-taper wavelength division multiplex (coupler B), and (3) the biconical-polished polarization maintaining fiber (coupler C), respectively. It is confirmed experimentally that the polarization characteristics of couplers A and B vary greatly with temperature, but those of coupler C are independent of temperature. Also, the wavelength dependence characteristics of the power splitting ratio of couplers B and C have almost no change with temperature. However, the wavelength dependence of coupler A is greatly changed with temperature. Comparing couplers A and B, it is postulated that the sinusoidal variations of the polarization state vs the incident polarization angle are due to the stress birefringence caused by the fiber twisting when the fused fiber coupler is fabricated and packaged.

Capacity upgrade in WDM submarine cable system

The capacity upgrade from 20 Gbit/s to 160 Gbit/s in a WDM submarine cable system has been designed based on the experimental study of the dependency of the repeater output power and the number of wavelength.

Wavelength demultiplexer for sub-nm channel optical amplifier WDM system

We proposed a practical wavelength demultiplexer for an optical amplifier wavelength division multiplexing (WDM) system using cascaded fiber gratings and optical circulators. Our proposed method can achieve a small excess loss and effective allocation of dispersion compensating for each channel, and introduce new channels without affecting other existing channels.

Correlation of the long-term performance fluctuation in 5 Gb/s, 2 WDM system

The long-term stability of the system performance is quite important to realize the practical system. In the long distance amplified lightwave system, the small fluctuations, such as polarization dependent gain and so on, cause the performance instability. In this letter, we report, for the first time, simultaneous performance measurements in the two-channel system operating at 5 Gb/s. It is shown that the correlation factor of the performance between the channels is described as a function of the channel separation.

Upgrade experiment on an installed optical amplifier submarine cable system

We have reported 12,000 km transmission at a bit rate of 5 Gbit/s on a middlehaul optical amplifier system before installation. This system is designed to operate with a single NRZ channel at 5 Gbit/s for 3,000 km transmission. In this paper, we report the transmission capability of the system after installation. By using a WDM technique, we have successfully transmitted 10 Gbit/s NRZ signals through 9,000 km.