Shinji Nagaoka

Synchro-scanned rotating tunable optical disk filter for wavelength discrimination

We propose a novel wavelength-discrimination scheme using a rotating tunable optical disk filter with a circularly graded cavity thickness. The transmittance peak of the filter varies linearly with the angular position of the beam on the disk while the bandwidth remains constant. The rotation is synchronized to an electrical signal, enabling temporal measurement of an optical spectrum. The first experimental demonstration was performed at 670 r/m using a filter that ranged from 1560 to 1615 nm under a 3-dB bandwidth of 5 nm. Single-mode laser light was correctly discriminated. Good linearity of the transmittance-peak variation was confirmed by analyzing the measured trace waveform.

Optical reflective filter with comb-drive nickel micromirror for optical fiber communication

A novel nickel micromirror with an electrostatic comb-drive actuator has been developed. It is fabricated by nickel surface micromachining, which features a thick photoresist molding process and nickel electroplating. It has a precise controllability and a wide tuning range. As an example of an application to optical communications, an optical reflective filter, which is an etalon constructed of a flat-end optical fiber facet and the micromirror, is demonstrated.

Microelectromechanical systems (MEMS) and their photonic application

THe fabrication of tunable optical devices by using Si free- space micro-optics and Ni micromirrors has demonstrated the applicability of MEMS technologies to photonic devices. Compact, multi-functional, assembly-free, micro-optical systems have been developed by using MEMS technologies to integrate optical devices and micromechanics onto the same wafer. A high aspect-ratio Si plate which works as a beam splitter has been fabricated using Si micromachining. A tunable laser diode with an external Si mirror has been fabricated and shown to have wavelength tunability. A Ni micromirror with comb-drive actuator has been developed and applied it to both a tunable optical filter and a tunable laser diode. Due to the precise motion of the micromirror, accurate optical tunability has been obtained.

High-accuracy laser-wavelength detection using a synchro-scanned optical disk filter

A simple laser-wavelength detection method is presented based on time-domain signal analysis using a continuously tunable, wide-band synchro-scanned optical disk filter. A differential signal is defined between two light powers monitored ground the time corresponding to the laser wavelength of interest to detect the slight wavelength deviation. A maximum detection accuracy of /spl plusmn/100 MHz has been achieved using a filter with a 3-dB width of 0.83 nm.

Compact latching type PANDA fiber switch

A compact and low-polarization crosstalk 1/spl times/2 PANDA fiber switch has been developed by precisely aligning the principal axes between the facing fibers. It exhibits an insertion loss of 0.5 dB, a return loss of 42 dB, polarization crosstalk of -30 dB, and a driving power of 9 mW. High-switching reproducibility with a loss change of less than 0.1 dB and a crosstalk change of less than 2 dB were obtained during 10/sup 4/ switching operations.

Micromechanically controlled GT interferometer for optical-pulse narrowing

Abstract A micromechanically controlled Gires–Tournois interferometer (micro-GTI) is proposed for a tunable dispersive medium for use in optical-pulse compression. Its dispersive properties, which are controlled by comb-drive micromirror actuation, were theoretically and experimentally evaluated to verify its capability to generate ultra-short optical pulses. Pulse compression performed using this micro-GTI generated nearly transform-limited pulses with a duration of 0.43 ps.

Widely tunable mode-locked laser diodes using optical disk filter

We present a scheme for generating high-repetition-rate mode-locked optical pulses within a wide wavelength-tuning range. This scheme utilizes an external-cavity laser configuration with a disk-shaped bandpass filter (disk filter), which is set in the external cavity. The disk filter can tune its transmission wavelength by rotating parallel to the external mirror. This simple wavelength-tuning scheme allows a short external cavity, which is necessary for generating high-repetition-rate optical pulses. This paper describes a preliminary experimental demonstration exhibiting 100%-modulated mode-locked pulses at 8 GHz in the 1535-1587-nm range.

Compact Fiber Bragg Grating Tunable Filter Microheater Loading Type

nal. In our system with an enhanced digital RX module, even when the optical power of the video signal (Pvo) at point T (carrier frequency f,,‘ > 91 MHz, degree of modulation = 50%) was +1 dBm, no digital RX sensitivity penalty was observed. Let’s discuss the interference of the digital signal leaked into the video line on the video signal. Assuming that the optical power of the digital signal (Pdo) at Point T is -14 dBm/Ave, the intensity of the digital signal leaked into the video line (Pdv) is -35 dBm/Ave (Is of 20 dB is assumed), which is far lower than the sensitivity of a wide band analog video receiver. In our system an analog video receiver with a 2.5 GHz bandwidth and sensitivity of -25 dBm/Ave was used. No interference of the digital signal on the video quality was visually observed. In conclusion, we have successfully demonstrated that an ONU can be constructed using a low cost WDM splitter by electrically enhancing the isolation between digital and video signals, thus establishing further feasibility for a lowcost consumer ONU.

Polarization-insensitive, wideband synchro-scan rotating optical disk filter for fast wavelength discrimination

Broadband photonic networks based on WDM supported by wideband amplifiers are important to provide flexible multimedia services. One of the key devices for them is an optical filter with various functions including wavelength discrimination for monitoring the multiplexed channels. Although many filters, e.g., acousto-optic filters and electrically tuned Fabry-Perot etalons, have been presented, they cannot simultaneously satisfy all the practical requirements such as polarization insensitivity, wide tunability, and quick, high stability operation due to their individual drawbacks. The rotary motion of a disk promises high-speed performance as demonstrated in hard-disk system. Here, we present and demonstrate a novel fast-filtering scheme using a synchro-scan rotating tunable disk filter with a circularly wedged interference layer, which has the merits of interference filters. The wavelength discrimination performance of this scheme was tested.