Semiconductor laser module and optical fiber amplifier

A semiconductor laser module, comprising:

• a semiconductor laser having an active region between a light-reflecting surface and a light-exit surface thereof;
• an optical fiber optically coupled to said semiconductor laser and including an optical fiber diffraction grating, said optical fiber diffraction grating serving to selectively reflect light within a predetermined wavelength band, wherein the wavelength band has a width larger than a wavelength interval of a longitudinal mode of light resonating between said light-reflecting surface and said light-exit surface
• a package having said semiconductor laser arranged therein;
• a Peltier element thermally connected to said semiconductor laser and arranged in said package;
• a first lens arranged in said package to oppose said light-exit surface of said semiconductor laser;
• and
• a second lens arranged outside said package to oppose said first lens,
• wherein positions of said light-exit surface, said first lens, said second lens, and said optical fiber diffraction grating are fixed.

An optical fiber amplifier comprising:

• a semiconductor laser module comprising:
• (a) a semiconductor laser having an active region between a light-reflecting surface and a light-exit surface thereof;
• and
• (b) an optical fiber optically coupled to said semiconductor laser and including an optical fiber diffraction grating, said optical fiber diffraction grating serving to selectively reflect light within a predetermined wavelength band, wherein the wavelength band has a width larger than a wavelength interval of a longitudinal mode of light resonating between said light-reflecting surface and said light-exit surface
• an ebrium-doped fiber;
• and
• a wavelength multiplexer/demultiplexer for optically coupling said semiconductor laser and said erbium-doped fiber to each other through said optical fiber.

An optical fiber amplifier comprising:

• a semiconductor laser module comprising:
• (a) a semiconductor laser having an active region between a light-reflecting surface and a light-exit surface thereof for emitting light within a 1.48-.mu.m band;
• and
• (b) an optical fiber optically coupled to said semiconductor laser and including an optical fiber diffraction grating, said optical fiber diffraction grating serving to selectively reflect light within a predetermined wavelength band of 2 nm to 5 nm, wherein the wavelength band has a width larger than a wavelength interval of a longitudinal mode of light resonating between said light-reflecting surface and said light-exit surface;
• an erbium-doped fiber;
• and
• a wavelength multiplexer/demultiplexer for optically coupling said semiconductor laser and said erbium-doped fiber to each other through said optical fiber.