Shigefumi Masuda

Photonic highway: broad-band ring subscriber loops using optical signal processing

The introduction of optical signal processing technology into transmission systems and basic experiments with optical drop/insert using bistable laser diodes are discussed. With broadband integrated services digital network (B-ISDN) architecture and technology now under study, optical signal processing (OSP) is being considered to increase network capacity and flexibility. B-ISDN will require over 40 Gb/s in the feeder loop that connects the central office and remote terminals having drop/insert function. Remote terminals will process large amounts of high-speed data. An OSP-based broadband subscriber loop photonic highway that uses a ring architecture linking photonic access nodes (PANs) that directly process optical signals is proposed. Each PAN has an optical drop/insert function and can synchronize optical frame signals using a proposed optical sampling memory. Optical drop/insert experiments confirmed the feasibility of the proposed method. >

All-optical data-latch experiments for photonic access nodes in the photonic highway

Abstract A novel approach to direct access at the optical level is proposed. We conducted experiments on all-optical data-latch functions using bistable laser diodes (LDs) for all-optical droplinsert operation in a 50-Mbitls data highway.

Polarization-Preserving Fiber-Optic 2X2 Directional Coupler

A low loss, wideband, compact, polarization-preserving fiber-optic directional coupler (PPFDC) has been developed for use in future coherent optical fiber transmission systems or gyroscopes. The PPFDC is made of two 200-pm-diameter sapphire ball lenses, a 3dB beam splitter, and four conical alumina-ceramic ferrules with flat reference planes to preserve polarization at the connection of the fibers. Built-in thermal stress change in the fiber is minimized because the fiber is polished only for the short length within the straight ferrule. The optical and mechanical axes are tilted, so cross-talk light from the fiber endfaces or lens surfaces is avoided. The optical directivity of the PPFDC is more than 50 dB, and return loss is more than 40 dB in the 1.3 kim wavelength region. The excess loss is less than 1 dB in the 1.2 to 1.4 Am wavelength range. The extinction ratio is more than 25 dB. The length of the coupling region of the PPFDC is about 1 mm including the two ball lenses and beam splitter. Spectral linewidths of a fiber-interfaced distributed-feedback (DFB) laser diode are measured by a delayed self-homodyne detection scheme, using the PPFDC. Experimental results of a novel polarization-preserving fiber-optic gyroscope using a phase-modulating PPFDC showed reasonable sensitivity and stability. These experimental results verified the above-mentioned characteristics of the PPFDC.

Polarization Preserving Fiber-Optic 2X2 Directional Coupler (PPFDC)

A low-loss, wide band, compact, polarization preserving, fiber optic directional coupler (PPFDC) is developed for use in future coherent optical fiber transmission systems or gyroscopes. The PPFDC is made of two 200 μm diameter sapphire ball lenses, a half-mirror and four conical alumina-ceramic ferrules with flat reference plane to preserve polarization at the connection of the fibers. Built-in thermal stress change in the fiber is minimized, because the fiber is polished only for the short length within the straight ferrule. The optical and mechanical axes are tilted, so cross-talk light from the fiber endfaces or lens surfaces is avoided. The optical directivity of the PPFDC is over 50 dB and return loss is over 40 dB in the 1.3 μm wavelength range. The excess loss is under 1 dB in the 1.2 to 1.4 μm wavelength range. The extinction ratio is over 25 dB. The length of the coupling region of the PPFDC is about 1 mm including the two ball lenses and half mirror. Spectral line widths of a fiber interfaced DFB laser diode are measured by a self delayed homodyne detection scheme, using the PPFDC. Experimental results of a novel polarization preserving fiber-optic gyroscope using a phase modulating PPFDC showed reasonable sensitivity and stability. These experimental results verified the above mentioned characteristics of the PPFDC.