The photodetection capabilities of 1.3- mu m channel substrate lasers are studied. The diodes can be used either as lasers or detectors in single-mode-fiber half-duplex communication links. As a detector, a responsivity of 0.26 A/W is obtained by efficiently coupling the input radiation into the facet using a lensed single-mode fiber. The spectral bandwidth extends from 1.1 to 1.37 mu m. The dark current at room temperature is 200 nA at 1-V bias and due in part to current leakage through the Fe-doped InP blocking layer. As lasers, the diodes have a frequency response of 4 GHz, and as detectors, the 3-dB bandwidth is 600 MHz. >

Characteristics of 1.3- mu m InGaAsP lasers used as photodetectors

An optical isolator for laser-to-single-mode fiber coupling is discussed. The coupling unit consists of a confocal two-lens system with a spherical glass lens and a planoconvex lens which is made of yttrium iron garnet (YIG). To minimize the number of elements, the YIG lens is used as a Faraday rotator as well as a coupling lens. Nevertheless, the planoconvex YIG lens satisfies the requirements of high coupling efficiency, high isolation, and low optical feedback from the Faraday rotator. The arrangement is theoretically and experimentally investigated. At a coupling efficiency of 34%, the total optical feedback into the laser diode was measured to be about -60 dB. >

A compact optical isolator with a plano-convex YIG lens for laser-to-fiber coupling

A new WDM (wavelength division multiplexing transmission configuration for local communications is proposed. In this configuration, the demultiplexing function is performed using narrow spectral sensitivity optical detectors and a demultiplexer is not required, allowing economical and simple WDM transmission. Dual-wavelength WDM transmission of 0.86 ?m and 0.73 ?m over 2 km on GI fibre is experimentally confirmed, using commercially available LEDs for both optical sources and detectors.

N. Aragaki

Papers

Proposal for simplified WDM transmission configuration