Masayuki Shigematsu

Erbium-doped fiber amplifier pumped at 1.48 mu m with extremely high efficiency

An erbium-doped fiber amplifier pumped at 1.48 mu m with extremely high efficiency has been developed. The fiber has a relative refractive index difference of 2.0% and Er/sup 3+/ ions and alumina are doped only in a limited area of the core. A slope efficiency of 86% and a gain coefficient of 6.3 dB/mW have been achieved by 1.48 mu m pumping along with excellent spectral signal output performance. In spite of its small mode-field diameter, it is possible to fusion-splice the fiber to standard dispersion-shifted fibers with low loss due to diffusion of fluorine dopant in the classing.<<ETX>>

Raman amplification over 100 nm-bandwidth with dispersion and dispersion slope compensation for conventional single mode fiber

We realized a discrete Raman repeater with the dispersion and dispersion slope compensation over seamless bandwidth of 100 nm by using DCF. The gain flatness after transmitting the transmission line was 2.3 dBp-p, and the OSNR was from 34.5 dB to 39.3 dB. We also estimated the improvement of gain flatness by using nine wavelengths of pumping lights, and we theoretically realized the 0.5 dB gain flatness Raman amplifier.

Highly nonlinear fiber-based lumped fiber Raman amplifier for CWDM transmission systems

The highly nonlinear fiber (HNLF)-based lumped fiber Raman amplifiers (LRAs) for four- and eight-channel coarse wavelength division multiplexing (CWDM) transmission systems have been investigated. By using the developed LRA, the four-channel CWDM transmission over conventional single-mode fiber (SMF) with the length of 150 km has been successfully achieved.

Hybrid dispersion compensating Raman amplifier module employing highly nonlinear fiber

Dispersion compensating Raman amplifier with reduced power consumption has been demonstrated employing a hybrid configuration comprising DCF and highly nonlinear fiber.

Wavelength dependence of dynamic gain fluctuation in a high-speed automatic gain controlled erbium-doped fiber amplifier

We have investigated the wavelength dependence of dynamic gain fluctuation in a high-speed automatic gain controlled erbium-doped fiber amplifier. The gain overshoot of a surviving channel owing to dropping channels increases slightly with decreasing surviving channel wavelength. On the other hand, the gain undershoot of a surviving channel caused by adding channels increases drastically at wavelengths shorter than 1536 nm, while that which remains is almost constant for wavelengths longer than 1536 nm. This sudden change in the wavelength dependence of the gain undershoot is caused by the wavelength dependence of the spectral-hole burning.

Impact of double rayleigh backscattering in discrete fiber Raman amplifiers employing highly nonlinear fiber

The feasibility of discrete Raman amplifiers employing HNLF (HNLFAs) has been examined by evaluating the DRBS characteristics. The HNLFA with the DRBS crosstalk of less than 35dB is demonstrated employing the optimized configuration.

Distortion-free Optical Fiber Amplifier for Analog Transmission Based on Hybrid Erbium-doped Fiber Configuration

In optical analog transmission systems, spectral gain tilt of a constituent erbium-doped fiber amplifier(EDFA) is known to degrade signal distortions in combination with laser chirping[1]. It has been suggested that the gain-tilt-induced signal distortions can be suppressed by reducing the EDF length [2] or inserting a tilt compensating filter [3] at the expense of an output power.

Wide-dynamic-range and channel-count-free thulium doped fiber amplifiers employing variable slope attenuation compensators designed for photonic networks

This paper presents the unique behavior of thulium doped fiber amplifiers (TDFAs) under circumstantial changes in the multi-wavelength photonic networking systems, namely in the span loss, the channel count, and the environmental temperature. Unlike EDFAs, TDFAs exhibit the dynamic gain-profile variation even when the gain-magnitude is fixed under the automatic gain control (AGC). In addition, it has been shown that the dynamic gain variation is less serious in the up-conversion pumping scheme. As a means to maintain the gain-profile of the up-conversion pumped TDFA, three techniques have been introduced and compared, namely: (i) the auxiliary pump around 1.56 μm, (ii) the mid-stage variable optical attenuator (VOA), and (iii) the mid-stage variable slope attenuation compensator (VASC). Employing the VASC, the output signal level has been successfully maintained within the error of 0.2 dB for the dynamic range of 8 dBp-p and the channel count from 4 to 32. Moreover, it has been shown that the temperature change also induces the gain tilt, which has been successfully compensated by the VASC with the level variation of less than 0.3 dB. In summary, the adjustable slope-compensating device will be useful to control the TDFAs under the various circumstantial changes.

A temperature-insensitive erbium-doped fiber amplifier for terrestrial wavelength-division-multiplexing systems

We have evaluated a variation in the temperature dependence of an erbium-doped fiber gain spectrum by a pump wavelength in the 980-nm band for the first time. By optimizing both the pump wavelength in the 980-nm band and a temperature-sensitive gain flattening filter, the gain change of an erbium-doped fiber amplifier was successfully suppressed to 0.18 dB/sub pp/ in the temperature range between 0/spl deg/C and 65/spl deg/C and the wavelength range of 37.0 nm.

A study of the control of Nd3+ energy levels in fluorozirconate glasses

Abstract Nd3+-doped ZBLAN single-mode fibers have been fabricated and optical amplification around 1340 nm has been obtained. However no gain has been observed in the 1300 nm region, which is used in most of the current telecommunication systems. This problem is because of the existence of the excited state absorption (ESA). In order to improve gain characteristics around 1300 nm, ESA and fluorescence wavelengths must be controlled by changing the ligand field around Nd3+ ions. Some Nd3+-doped fluorozirconate-based glasses, in which other alkali elements were substituted for Nd were prepared and absorption, fluorescence and lifetime characteristics of the Nd3+ ions in the glasses were examined. As a result, it was found that the ESA wavelength was shifted by the alkali elements systematically.