We have designed and fabricated a compact 4-array integrated SOA module using a novel parallel optical coupling scheme and polarization-insensitive built-in array isolators. We achieved ultra-high On/Off extinction ratio of more than 60 dB and low cross talk of better than -60 dB as well as high-isolation of over 47 dB in wide wavelength ranges. We also developed a wavelength-insensitive parallel optical coupling scheme and an efficient thermal dissipating structure for a 4-array SOA module. We applied these technologies into 4-array SOA module fabrication and demonstrated a uniform optical coupling with the loss variance of 1 dB over the 140-nm wavelength ranges. We also demonstrated simultaneous operation of 300 mA 4 channels with low thermal degradation of the module gain less than 1 dB.

We developed a compact, 16-channel integrated optical subscriber module for one-fiber bi-directional optical access systems. They can support more subscribers in a limited mounting space. For ultimate compactness, we created 8-channel integrated super-compact optical modules, 4-channel integrated limiting amplifiers, and 4-channel integrated LD drivers for Fast Ethernet. We introduce a new simulation method to analyze the electrical crosstalk that degrades sensitivity of the optical module. A new IC architecture is applied to reduce electrical crosstalk. We manufactured the optical subscriber module with these optical modules and ICs. Experiments confirm that the module offers a sensitivity of -27.3 dBm under 16-channel 125 Mbit/s simultaneous operation.

Aiming at lower cost and further miniaturization, we developed a new optical coupling system for use as an optical interface of a parallel optical interconnect module, called ParaBIT-1. It consists of a new-structure 24-fiber bare fiber (BF) connector whose main parts are made of molded plastic and a 24-channel optical coupling component using new polymeric optical waveguide film. To prevent bare fibers from breaking, the BF connector plug has a fiber protector. This BF connector can be joined by direct physical contact between bare fibers in fiber guide holes with a 250-µm pitch. The buckling forces of the fibers themselves secure the physical contacts. The average measured insertion loss of the 24-fiber BF connector was 0.05 dB, and the return losses were over 35 dB. The optical coupling components are composed of a 24-ch polymeric optical waveguide film with 45 mirrors and the 24-fiber BF connector interface, and can be assembled by passive alignment. The high thermal stability of the film allows soldering, and the film is fabricated by direct photo patterning. The average insertion losses of the components for transmitter and receiver modules were 1.28 and 1.35 dB, respectively.

Attempts have been made to evaluate and investigate the radiated emissions from fiber optical modules that are currently available in the market. Far electric field strength measurements show that the radiated emission has a peak at a high-order harmonic wave of the fundamental pulse frequency and reaches a level exceeding the limiting values of the CISPR noise specifications. Near magnetic field distribution measurements show that the source of the interference noise lies between a light emitting diode (LED) module and an LED driver. These measurements are compared with those of electromagnetic field calculations based on a high-frequency equivalent circuit. As a result, it was established that both the peaking effects of deformed pulse waves transmitted between an LED module and an LED driver and the radiation characteristics of the optical transmitter circuit act as factors for increasing the radiation level of the peak frequencies in the radiated emission from fiber optical modules.

A high-density multi-port optical connector that exploits the flexibility of bare optical fibers has been developed for use as an optical interface of a parallel optical interconnection module. In the BF (Bare-Fiber) connector, 24 multimode-fibers are mated by direct physical contact in micro-glass-capillaries with a 250-µm pitch. The buckling forces of the optical fibers themselves secure the physical contact. Optical fiber buckling is investigated theoretically and experimentally. A new design method to optimize the span length l and the longitudinal displacement ΔL for the buckling is also proposed based on the requirements afor optical characteristics, mechanical reliability, and dimensional tolerances, etc. A prototype BF connector with l 10 mm and ΔL of 50 µm was designed and fabricated for multimode fiber connections. This connector provides high optical performance: an average insertion loss of 0.05 dB and a return loss of over 35 dB at 850 nm. The optical performance remained stable after a durability test with ten connection-repetitions.

This paper describes packaging techniques based on a novel passive alignment technique as key techniques for module assembly. A laser diode (LD) is passively positioned by detecting a pair of alignment marks located on the LD and Si substrate. A single-mode fiber is self aligned on a Si V groove. A simple receptacle structure for the module output port is also newly designed. This structure is more suitable for the automatic assembly line as well as the module mounting process on circuit board. In this paper, an advanced module applications such as a hybrid integrated wave guide module and a surface mountable (SMT) LD module is introduced.

This paper describes the technological issues in achieving a low-cost hybrid WDM module for access network systems. The problems which should be resolved in developing a low-cost module are clarified from the viewpoint of the module assembly in mass production. A design concept for a low-cost module suitable for mass production is indicated, which simplifies the alignment between a laser diode and a waveguide, and reduces the number of the components such as lenses and mirrors. The low-cost module is achieved by employing a flip-chip bonding method with passive alignment using a spot-size converter integrated laser diode (SS-LD) and p-i-n waveguide photodiodes (WGPDs) on a planar lightwave circuit (PLC) platform. We confirm that the SS-LD and the WGPD provide high coupling efficiency with a large tolerance for passive alignment. To achieve a high-sensitivity receiver, the module is designed to employ an asymmetric PLC Y-splitter that prefers a PD responsivity to an LD output power because of the high-coupling efficiency of the LD, and to employ a bare preamplifier mounting to reduce the parasitic capacitance into a preamplifier. We also demonstrate the dynamic performance for a 50-Mb/s burst signal, such as a high sensitivity, an instantaneous AGC response, and a small APC deviation of the transceiver.