Shoichi Sudo

Fabrication of praseodymium‐doped arsenic sulfide chalcogenide fiber for 1.3‐μm fiber amplifiers

Pr3+‐doped As‐S chalcogenide fiber is fabricated using a double‐crucible method. The thermal and spectroscopic properties of Pr3+‐doped As‐S glasses are clarified. Pr3+‐doped As‐S fiber is shown to be a promising candidate that will lead to efficient Pr3+‐doped fiber amplifiers.

1.4-μm-band gain characteristics of a Tm-Ho-doped ZBLYAN fiber amplifier pumped in the 0.8-μm band

The gain characteristics of a 1.4-/spl mu/m-band thulium-holmium-doped ZBLYAN fiber amplifier are described. Signal gain is obtained over the whole 1.4-/spl mu/m band for a pump power level of 73.5 mW. A maximum signal gain of 18 dB is achieved at a signal wavelength of 6.46 /spl mu/m for a pump power of 150 mW at 0.79 /spl mu/m. The noise figure is 5.6 dB in the signal wavelength region from 1.45-1.50 /spl mu/m. From a comparison of the gain characteristics of thulium-holmium-doped ZBLYAN fibers and thulium-doped ZBLYAN fibers, it is proved that holmium ions play an effective role in increasing the gain and widening the gain spectrum.<<ETX>>

Optical amplification with neodymium-doped chalcogenide glass fiber

Optical amplification at 1.083 μm with neodymium-doped chalcogenide fiber is observed. The thermal and spectroscopic properties of a new chalcogenide glass system are measured in view of its potential use as a rare-earth host. A maximum internal gain of 6.8 dB is achieved for a pump power of 180 mW.

Development of an efficient praseodymium-doped fiber amplifier

This paper describes the development of an efficient praseodymium-doped fluoride fiber amplifier (PDFA) using newly developed PbF/sub 2/-InF/sub 3/-based fluoride single-mode fiber. First, the spectroscopic properties of Pr/sup 3+/ in PbF/sub 2/-InF/sub 3/-based and ZrF/sub 4/-based fluoride glass are compared and then the fabrication of high-NA PbF/sub 2/-InF/sub 3/-based fluoride single-mode fiber is presented. The gain coefficients obtained with the developed fiber are 0.36 dB/mW with a forward pumping scheme and 0.4 dB/mW with a bidirectional pumping scheme. We use this newly developed fiber to construct two types of an efficient PDFA module. We realized a 19-in rack size PDFA module with a master oscillator/power amplifier laser diode (MOPA-LD) and a plug-in type PDFA module with a wavelength-stabilized 1.017-/spl mu/m LD and describe their amplification characteristics.

35-dB gain Tm-doped ZBLYAN fiber amplifier operating at 1.65 μm

We demonstrate the first high gain rare-earth-doped fiber amplifier operating at 1.65 /spl mu/m. It consists of ZBLYAN fiber with a Tm/sup 3+/-doped core and Tb/sup 3+/-doped cladding, pumped by 1.22 /spl mu/m laser diodes. It is possible to achieve efficient amplification with Tm/sup 3+/ ions if their amplified spontaneous emission (ASE) in the 1.75 to 2.0 /spl mu/m wavelength region is suppressed by doping Tb/sup 3+/ ions in the cladding. A two-stage-type fiber amplifier is constructed and a signal gain of 35 dB is achieved for a pump power of 140 mW. A gain over 25 dB is realized in the 1.65 /spl mu/m to 1.67 /spl mu/m wavelength region.

28.3 dB gain 1.3 mu m-band Pr-doped fluoride fiber amplifier module pumped by 1.017 mu m InGaAs-LD's

A praseodymium (Pr)-doped fluoride fiber amplifier (PDFA) module that is pumped by strained quantum-well InGaAs laser diodes (LDs) is described. The amplifier module, consisting of a four LD pump configuration and a high NA Pr-doped fluoride fiber with low scattering loss, exhibits a maximum signal gain of 28.3 dB and a saturation output power of 6 dBm at a signal wavelength of 1.30 mu m. It is shown to be the most promising module for the 1.3- mu m-band optical amplifier.<<ETX>>

Pr/sup 3+/-doped fluoride fiber amplifier module pumped by a fiber coupled master oscillator/power amplifier laser diode

We constructed the first Pr/sup 3+/-doped fluoride fiber amplifier (PDFA) module pumped by a fiber-coupled master oscillator/power amplifier laser diode (MOPA-LD) operating at 1.017 /spl mu/m. The maximum signal gain and noise figure were 30.5 and 5.5 dB, respectively. An output power of 18 dBm was achieved at an input signal power of 0 dBm. Furthermore, we showed that the use of MOPA-LD pumping, rather than conventional Nd-YLF laser pumping, makes it possible to halve the length of the Pr/sup 3+/-doped fluoride required in the amplifier module and also allows a broader spectral bandwidth to be achieved.

Generation of 5 THz repetition optical pulses by modulation instability in optical fibers

5 THz repetition rate optical pulses have been achieved with modulation instability in an optical fiber. The detailed investigation on the relationship between fiber anomalous dispersion and modulation frequency enables high repetition rate optical pulses, yielding a control method of pulse repetition rate.

Efficient PDFA module using high-NA PbF 2 /InF 3 -based fluoride fiber

The highest reported single-pass gain coefficient of 0.36 dB/mW has been achieved using a newly developed Pr/sup 3+/-doped high-NA PbF/sub 2//InF/sub 3/-based fluoride fiber, with a /spl Delta/n of 6.6%, a core diameter of 1.2 /spl mu/m and a transmission loss of 250 dB/km at 1.2 /spl mu/m. This fiber was used to construct an efficient PDFA module with a MOPA-LD. A small-signal net gain of 22.5 dB was achieved at 1.30 /spl mu/m with a pump power of 23m mW.

Low-noise operation of fluoride-based erbium-doped fiber amplifiers with 4 I 11/2 -level pumping

The low-noise operation of fluoride-based erbium-doped fiber amplifiers (EDFAs) is demonstrated with (4)I(11/2)-level pumping for what we believe to be the first time. A noise figure as low as 3.5 +/- 0.5 dB at 1550 nm is achieved by means of 970-nm pumping. It is shown that it is possible to construct fluoride-based EDFAs with a noise figure as low as that of silica-based EDFAs.