Tunable Wavelength Filter Research Articles

Frequency tracking of tunable liquid-crystal wavelength filter for WDM transmission

The authors show that the drift in the pass-band of a liquid crystal Fabry-Perot tunable filter caused by temperature variations can be controlled by using electronic feedback. The circuit locks onto the wavelength of the incoming signal and adjusts the drive voltage that is applied to the liquid crystal to compensate for any shifts. Bit-error-rate measurements were used to show that the use of such feedback can extend the operating temperature range by tens of degrees. The purpose was to investigate the effect of this modulation on the bit-error-rate in a data transmission system.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

1.5 µm Semiconductor Wavelength Tunable Optical Filter Using a λ/4-Shifted Passive Waveguide Grating Resonator

A 1.5 µm semiconductor wavelength tunable optical filter using a λ/4-shifted passive waveguide grating resonator has been developed. Both wavelength channel number and transmissivity are analyzed with respect to grating coupling coefficient, filter length, and waveguide loss. The influence of facet reflectivity and phase-shift value on transmissivity and wavelength channel number are also investigated. A wavelength shift as wide as 42 Å is able to be obtained by carrier injection with the fabricated filter.

Random access protocols for high-speed interprocessor communication based on an optical passive star topology

A multiple-instruction multiple-data (MIMD) distributed memory parallel computer system environment is considered. Media access control protocols that maintain good performance with high capacity optical channels are investigated. Three examples of star-coupled structures are introduced, one of which exhibits optical self-routing. Self-routing single-step optically interconnected communication structures can be designed through the incorporation of agile laser diode sources and wavelength tunable optical filters in a wavelength-division multiple-access environment. Intermediary latencies typical of MIMD distributed memory systems are eliminated. The degree and diameter of the resulting structures are dramatically reduced, and the complexity of the communication subsystem is reduced since intermediate buffering and routing of packets are eliminated. >

Semiconductor photonic functional devices

Recent advances in semiconductor photonic functional devices based on the nonlinearities of laser diodes (LDs) are reviewed. Because the current research is driven primarily by the needs of optical fiber communications systems, most devices are made of InGaAsP and operate at wavelengths of between 1.3 and 1.55 mu m, the wavelength window in which optical fibers have their most favorable properties. Minimum loss is at 1.55 mu m, and zero dispersion is at 1.3 mu m. AlGaAs devices operating at around 0.85 mu m have also been reported. Two types of optical bistability-absorptive and dispersive-are explained, and devices based on them are described. Switching characteristics of bistable devices are discussed. Tunable wavelength converters and filters are also examined. Applications to all-optical communication and to optical switching systems are considered. Directions for future development are indicated. >

Applications of optical integrated circuits to signal processing. Semiconductor Optical Functional Devices.

Optical functional devices are indispensable for light signal processing systems. So far, various functions have been realized by use of integrated configuration of semiconductor optical devices, This paper descrides progress in semiconductor optical functonal devices based on semicoductuctor laser diodes and their application to ligh signal processing. First, it is shown that memory operation can be demonstrated with a bistable laser diode with a tandem electrode structure, and then ultra-opical flip-ffop operation of a bistable laser diode is introduced. Second, a wavelength converter laser and a tunable wavelength filter, which are thought to be promising for wavelength division switching networks, ar descrideb. Finally, it is shown that various optical logic operations can be attained by using the bistable laser diode.

A photonic wavelength-division switching system using tunable laser diode filters

A photonic wavelength-division switching system using semiconductor tunable wavelength filters is proposed. A switching system using wavelength switches and multistage switching networks is discussed. A crucial point in developing this switching system is to achieve a large number of wavelength-division channels. The potential of 100 wavelength-division channels in such switching systems is estimated, based on InP optical integrated circuits. A wavelength network synchronization which permits the network to utilize such a large number of wavelength-division channels without wavelength misalignment and drift is proposed. An eight-channel wavelength-division switching experiment, using phase-shift-controlled distributed feedback laser diodes as tunable wavelength filters, is reported. >

Line capacity expansion schemes in photonic switching

Design considerations for capacity expansion are described, and requirements for photonic switch matrices, optical memories, and tunable-wavelength filters are examined. The present status of photonic switching devices and system experiments is discussed, covering space-, wavelength-, and time-division switches. Hybrid switching systems and coherent optical detection are considered as examples of system technology that will facilitate line capacity expansion. >

A coherent photonic wavelength-division switching system for broad-band networks

A coherent photonic wavelength-division (WD) switching system, utilizing a coherent wavelength switch ( lambda switch), is proposed. In the proposed coherent lambda switch, the tunable wavelength filter function is accomplished using coherent optical detection with a wavelength tunable local oscillator. The coherent photonic WD switching system has the following features; (1) low crosstalk switching for dense WDM signal, and (2) large line capacity capability. Design considerations show that 32 wavelength division channels can be available with a coherent lambda switch. It is also shown that a broadband metropolitan-area-network with over 1000 line capacity is possible, using a multistage connection in the coherent lambda switches. The switching function of the coherent lambda switch is demonstrated in a two-channel wavelength-synchronized switching experiment, using 8-GHz-spaced, 280-Mb/s optical FSK signals.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Integrated optical. acoustically tunable wavelength filter

A TM/TE convenor is combined with a TE-pass polariser on a common LiNbO3 chip to obtain an integrated optical, acoustically tunable wavelength filter. Its tuning range is 1.45–1.57 μm wavelength with a filter half-width of 2.8 nm. Owing to the combined acoustical/optical strip guide structure used in the mode convenor, a very low acoustic drive power of only 9 mW is required.

Voltage tunable LiNbO_3 wavelength filters

We describe here the design and operation of voltage tunable wavelength filters fabricated in titanium diffused LiNbO(3). The devices, based on the nonsymmetric interferometer, have channel separations of 11-31 nm at lambda= 1300 nm, and tuning rates of 3-10 nm/V. The periodic wavelength response of these filters allows them to be cascaded to combine or separate 2(N) channels in N stages.

1.5 μm tunable wavelength filter using a phase-shift-controlled distributed feedback laser diode with a wide tuning range and a high constant gain

We demonstrate a 1.5 μm tunable wavelength filter which uses a newly developed phase-shift-controlled distributed feedback laser diode. A tuning range as wide as 120 GHz (9.5 Å) with 24.5 dB constant gain has been achieved. An 18-channel wavelength selection with less than −10 dB crosstalk is expected with this filter.

Electronic wavelength tuning using acoustooptic tunable filter with broad continuous tuning range and narrow channel spacing

The use of acoustooptic tunable filters as tunable-wavelength filters in a multiwavelength network is reported. Fast ( approximately=3 mu s access time), broad, continuous tuning (1.3-1.56 mu m) and narrow channel spacing (4.5 nm) in a nine-channel distribution system were demonstrated. The combination of broad tuning range and narrow channel spacing allows channel selection in a distribution system with hundreds of wide-band wavelength-division-multiplexed channels. The wavelength switching time, measured as approximately=3 mu s, is important in many high-speed switching applications. >

1.5 μm tunable wavelength filter with wide tuning range and high constant gain using a phase-controlled distributed feedback laser diode

We demonstrate a 1.5 μm tunable wavelength filter which uses a phase-controlled distributed feedback laser diode. Tuning range as wide as 43 GHz (3.4 Å) with 27 dB constant gain has been achieved. A five-channel wavelength selection with less than −10 dB crosstalk is expected with this filter.

Tunable wavelength filters using λ/4-shifted waveguide grating resonators

We report on wide tuning range 1.5 μm wavelength filters using λ/4-shifted waveguide grating resonators. A tuning range of a transmission resonance wavelength as wide as 42 Å by carrier injection and two-channel wavelength signal switching was achieved.

Polarization-independent electro-optically tunable narrow-band wavelength filter

We propose and demonstrate the first polarization-independent electro-optically tunable wavelengh filter with single-mode waveguides. The Ti:LiNbO3 filter utilizes narrow-band electro-optic TE ↔ TM conversion and employs TE/TM polarization splitters in the input and output waveguides. The filter operates at 1.52 μm with a bandwidth of only 12 Å and can be electro-optically tuned over at least 110 Å at a tuning rate of 0.55 Å/V.

1.5 μm λ/4-shifted DFB LD filter and 100 Mbit/s two-channel wavelength signal switching

A 1.5 μm tunable wavelength filter was studied. A 1.5 μ λ/4-shifted distributed feedback laser diode (DFB LD) was applied as an effective single wavelength selective filter. A wavelength switching experiment in a 100 Mbit/s two-channel wavelength multiplexed system was successfully demonstrated by using the tunable λ/4 shifted DFB LD filter.

Semiconductor devices in photonic switching

Three types of photonic switching networks have been proposed, namely, optical space-division switching, optical wavelength-division switching. Optional function devices required for each switching network are as follows: optical switch matrix for space-division switching; optical memory and optical write/read gate for time-division switching; and tunable wavelength filter and wavelength converter for wavelength-division switching. Recent progress in semiconductor functional devices such as modulators, switching devices, bistable devices, and wavelength control devices, which would be key devices to build switching networks, is reviewed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Zero order anomaly of dielectric coated gratings

The zeroeth order diffraction efficiency of a three-layer dielectric grating is studied theoretically and experimentally. A sharp resonance anomaly due to the excitation of guided waves is observed, which increases significantly the reflectance of the system. The operation of the structure as a tunable narrow-band wavelength filter in a reflection regime is demonstrated.