Nippon Telegraph and Telephone Corporation

Ntt Electronics Corporation

Yoshiki Nishida

Osamu Tadanaga

Masaki Asobe

Hiroyuki Suzuki

Hiroshi Miyazawa

Tsutomu Yanagawa

Shoichi Sudo

Terutoshi Kanamori

Yasutake Ohishi

Hiroyasu Mawatari

Junji Yumoto

Atsushi Mori

Tadashi Sakamoto

Eishi Kubota

Kaoru Yoshino

Hirohisa Kanbara

Katsuaki Magari

Takeshi Umeki

Hiroji Masuda

Shinichi Aozasa

Makoto Shimizu

A wavelength converter which performs simultaneously wavelength conversion for a plurality of input light wavelengths that are unequally intervals, is provided. The nonlinear material of the wavelength converter has a modulation structure which has modulation of a nonlinear optical constant at a period &#x39b;in a propagating direction of light, a phase being continuously changed each period &#x39b;and a continuous phase modulation for a different period &#x39b;being added to the modulation structure. The nonlinear material has a modulation structure obtained by changing a modulation curve for the phase modulation, wherein a phase mismatch &#x394;&#x3b2; is represented by &#x394;&#x3b2;=2&#x3c0;(n/&#x3bb;&#x2212;n/&#x3bb;&#x2212;n/&#x3bb;), and at least three peaks at unequally intervals within a plurality of peaks for conversion efficiency represented by 2&#x3c0;/&#x39b;+2&#x3c0;i/&#x39b;(i=m, m+1, . . . , n: where m and n are positive or negative integers) have highest conversion efficiency.

Wavelength converter and wavelength conversion apparatus

A light source apparatus with modulation function has a wavelength conversion module () composed of a nonlinear optical material with a structure having a nonlinear constant modulated periodically. It outputs a difference frequency or sum frequency produced by multiplexing pumping light from semiconductor laser light sources () and () with different wavelengths through a WDM coupler () and by launching the multiplexed light into the optical waveguide. The semiconductor laser light source () includes a diffraction grating. The semiconductor laser light source () includes a section for modulating output light emitted from its semiconductor laser, and is connected to an external FBG () which has a reflection band narrower than a resonance wavelength spacing determined by the device length of the semiconductor laser. The FBG () is supplied with the modulated output.

Light source apparatus with modulation function and its driving method

A laser light source is disclosed consisting of first and second lasers that respectively generate laser beams of wavelengths &#x3bb;and &#x3bb;. Wavelength &#x3bb;is in the range of 0.9-1.0 &#x3bc;m. A nonlinear optical crystal uses the laser beams of wavelengths &#x3bb;and &#x3bb;as inputs, and outputs a coherent beam having a wavelength &#x3bb;of a difference frequency that satisfies a relationship of 1/&#x3bb;&#x2212;1/&#x3bb;=1/&#x3bb;. The nonlinear optical crystal has a periodically poled structure of a single period. The wavelength &#x3bb;of the difference frequency varies between 3.1 &#x3bc;m and 2.0 &#x3bc;m when the wavelength &#x3bb;varies between 1.3 &#x3bc;m and 1.8 &#x3bc;m.

Laser light source

The invention provides a compact laser light source whose wavelength can be designed freely in a wavelength band in which the semiconductor laser has not been put to practical use by combining an efficient nonlinear optical crystal and high-power semiconductor lasers for optical communication. In one embodiment, the laser light source includes: a first laser for generating a laser beam of a wavelength &#x3bb;; a second laser for generating a laser beam of a wavelength &#x3bb;; and a nonlinear optical crystal that allows the laser beam of wavelength &#x3bb;and the laser beam of wavelength &#x3bb;as inputs and outputs a coherent beam having a wavelength &#x3bb;of a sum frequency that satisfies a relationship of 1/&#x3bb;+1/&#x3bb;=1/&#x3bb;. The wavelength &#x3bb;of the sum frequency is 589.3&#xb1;2 nm that is equivalent to the sodium D line.

A wavelength converter has a phase modulated periodically modulated structure, where a nonlinear optical coefficient is periodically modulated at a fundamental period &Lgr; and the phase of the modulation varies nearly continuously, and the phase variation of the modulation unit structure is repeated at a period &Lgr; (>&Lgr; ). A conversion efficiency is made maximum when a phase mismatch amount &Dgr;&bgr; equals 2&pgr;/&Lgr; &plusmn;2&pgr;i/&Lgr; (i&equals;0, 1, . . . , n, where n is a positive integer), 2&pgr;/&Lgr; &plusmn;2&pgr;(2i&plus;1)/&Lgr; (i&equals;0, 1, . . . , n), or 2&pgr;/&Lgr; &plus;2&pgr;i/&Lgr; (i&equals;m, m&plus;1, . . . . n, where m and n are positive or negative integers satisfying &verbar;m&verbar;&ne;&verbar;n&verbar;), thereby providing a wavelength converter and wavelength converting apparatus that can be designed to be able to cope with a desired number of pump wavelengths, prevent the reduction in the conversion efficiency, and be configured easily using a practical size of a nonlinear optical material.

Wavelength converter and wavelength converting apparatus

An optical fiber amplifier with a high conversion efficiency, which is capable of using the pump light in the wavelength band that can be emitted by the laser diode, is formed by an amplification optical fiber containing thulium at least in a core, to which a signal light is to be entered, and a pump light input unit configured to enter at least one pump light with a wavelength in a range of 1320-1520 nm, or more preferably 1320-1480 nm, into the amplification optical amplifier.

Thulium-doped fiber amplifier using pump light for improving conversion efficiency in a S-band

This invention relates to fluoride glass with a specific composition having wide infrared transmission. A fluoride optical fiber using this fluoride glass can give high efficiency with a low loss. The fluoride optical fiber having a second cladding on the outer periphery of a first cladding can adjust the refractive index of the first cladding suitably.

Fluoride glass fiber

Fluoride glass-based optical fiber for an optical amplifier which contains rare earth metal ions in the core glass has a relative refractive index difference .DELTA.n between the core and the cladding of 1.4% or more. The core glass contains PbF.sub.2 in a proportion of 25 mol % or less based on the total composition of the core glass. The fluoride glass is doped with rare earth metal ions, and part of the fluorine in the glass may be substituted by at least one halogen Pr.sup.3+, Pr.sup.3+ --Yb.sup.3+, Pr.sup.3+ --Nd.sup.3+, or Pr.sup.3+ --Er.sup.3+ can be doped as the rare earth metal ions. Chlorine, bromine or iodine may be used as the halogen.

Optical fiber for optical amplifier

Fluoride glass-based optical fiber for an optical amplifier which contains rare earth metal ions in the core glass has a relative refractive index difference .DELTA..sub.n between the core and the cladding of 1.4% or more. The core glass contains PbF.sub.2 in a proportion of 25 mol % or less based on the total composition of the core glass . The fluoride glass is doped with rare earth metal ions, and part of the fluorine in the glass may be substituted by at least one halogen. Pr.sup.3+, Pr.sup.3+ --Yb.sup.3+, Pr.sup.3+ --Nd.sup.3+, or Pr.sup.3+ --Er.sup.3+ can be doped as the rare earth metal ions. Chlorine, bromine or iodine may be used as the halogen.

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Mito, Japan

Yoshiki Nishida