Abstract: An optical transmitting apparatus includes semiconductor laser elements. Upon receiving laser beams, a multiplexed beam is emitted from a wavelength multiplexing filter. The wavelength multiplexing filter includes a triangular prism and a wavelength multiplexing filter film. A front end face and a rear end face of the prism are not parallel to each other so that a prism angle at which a surface parallel to the front end face intersects a surface parallel to the rear end face, is an acute angle. The prism angle is the angle at which the laser beam impinging from the front end face into the triangular prism is reflected by the wavelength multiplexing filter film toward the front end face and the multiplexed beam is directed to the optical axis side of the optical fiber.

Abstract: An optical transmitting apparatus includes semiconductor laser elements. Upon receiving laser beams, a multiplexed beam is emitted from a wavelength multiplexing filter. The wavelength multiplexing filter includes a triangular prism and a wavelength multiplexing filter film. A front end face and a rear end face of the prism are not parallel to each other so that a prism angle at which a surface parallel to the front end face intersects a surface parallel to the rear end face, is an acute angle. The prism angle is the angle at which the laser beam impinging from the front end face into the triangular prism is reflected by the wavelength multiplexing filter film toward the front end face and the multiplexed beam is directed to the optical axis side of the optical fiber.

Abstract: An optical isolator is secured so that a direction of polarization permitted to pass through the optical isolator is angled against a direction of polarization of a laser beam entering the optical isolator so that the laser beam transmitted by the optical isolator is attenuated and an optical output from an optical fiber, located at a maximum coupling point, is at a desired level.

Abstract: A laser diode module provides methods for coupling laser light and optical fiber which achieve a higher coupling efficiency than conventional methods and is cheaper and easier to assemble without losing conventional high-frequency power supply function. In a laser diode module, a high-frequency electric line 11 to a laser diode is located on the upper surface of a photodiode carrier 4 for supporting a photodiode 3; the photodiode carrier 4 is large with a trapezoidal shape. This shape prevents the surface of the photodiode 3 from returning to the laser diode reflected light emitted from the rear of the laser diode 1. A spherical convexo-plane lens 27 is located so that its spherical surface faces the laser diode 1 and is held on a lens holder 22 with a cylindrical hole at an optimum angle to a slant end of an optical fiber core 23 so that a center of curvature 29 of the spherical surface is on an optical axis 19 of laser light which is collimated by a collimating lens 7.