Hitachi, Ltd.

Hitachi Communication System, Inc.

Atsushi Murata

Satoshi Aoki

Tsuyoshi Tanaka

Kazuo Yamaguchi

Kazumi Kawamoto

Nobuhiro Matsudaira

Naohiko Baba

Kazuo Aoyama

Takashi Minato

Tsutomu Yoshiya

Shinzoo Nishiyama

Kyouichi Yamamoto

Yuuki Sato

A method of manufacturing an optic transmission module assures a high reliability for the module by inspecting the character of a low bit error rate (BER) of the module quickly and accurately. The module is employed in an optical communication system (light transmission system) required to cope with information communication systems that are becoming faster and faster in operation and larger and larger in capacity. Also disclosed is a system and a method for inspection of the BER character which uses a rectangular wave pulse as an interference light to calculate a degradation quantity of a signal-to-noise ratio (S/N) on the basis of a simple theory, thereby inspecting the BER character by extrapolating a case in which there is no interference light (S/X&equals;&infin; or X&equals;0) with use of a sign error rate theoretical value according to a bit error rate of a light signal measured according to the degradation quantity.

Method for manufacturing optic transmission modules and system for inspecting bit error rate characters

An optical transmitter can communicate at a transmission speed exceeding Gb/s with a low bit error rate. An optical transmission module includes a semiconductor module having a semiconductor laser and an impedance matching element, a driver circuit for driving the semiconductor laser to emit an optical signal, and an optical fiber for transmitting the optical signal. The impedance matching element matches an impedance of the semiconductor laser module to an impedance of the driver circuit. The optical transmission module includes an impedance element for reducing an input impedance of the semiconductor laser module as viewed from the driving circuit in order to reduce a fall time of the optical signal. Impedance matching elements and are added to remove possible mismatching between the module and the driver circuit caused by a manufacturing error and to improve the yield of the module.

Optical transmission module

In a semiconductor laser module with a built-in optical isolator which isolator consists of a polarizer, a Faraday rotator and an analyzer, an optical refraction sheet having a wedge-shaped section is disposed on the beam incidence side of the polarizer. Accordingly, even when the mechanical center axis of the optical isolator is placed to be in parallel with the optical axis of the semiconductor laser or in other words, even when the beam incidence-outgoing surfaces of the polarizer, Faraday rotator and analyzer are placed to be vertical to the incident parallel beams, the parallel beams incident into the optical isolator are refracted by the optical refraction sheet having the wedge-shaped section, so that the parallel beams passing through the beam incidience-outgoing surfaces of the polarizer, Faraday rotator and analyzer do not pass vertically and the return of reflected beams to the semiconductor laser can be thus reduced.

Semiconductor laser module with built-in optical isolator

A semiconductor laser module containing a semiconductor laser therein is disclosed, in which the insulated conductor of a coaxial-type high-frequency connector fixed to the outer wall suface of a dual in-line package is connected to an airtight terminal mounted on the package and connected electrically with the semiconductor laser in the package. Thus, a high-frequency signal in the giga bit band can be readily applied to the semiconductor laser through the coaxial-type high-frequency connector, without degrading the airtightness of the dual in-line package.

Semiconductor laser module of dual in-line package type including

Growing community of inventors

Yokohama, Japan

Atsushi Murata