The very broad bandwidth of low-loss optical transmission in a single-mode fiber and the recent improvements in single-frequency tunable lasers have stimulated significant advances in dense wavelength division multiplexed optical networks This technology, including wavelength-sensitive optical switching and routing elements and passive optical elements, has made it possible to consider the use of wavelength as another dimension, in addition to time and space, in network and switch design The independence of optical signals at different wavelengths makes this a natural choice for multiple-access networks, for applications which benefit from shared transmission media, and for networks in which very large throughputs are required Recent progress in multiwavelength networks are reviewed, some of the limitations which affect the performance of such networks are discussed, and examples of several network and switch proposals based on these ideas are presented Discussed also are critical technologies that are essential to progress in this field >

Dense wavelength division multiplexing networks: principles and applications

A lithographic apparatus configured to project a patterned beam of radiation onto a target portion of a substrate is disclosed. The apparatus includes a first radiation dose detector and a second radiation dose detector, each detector comprising a secondary electron emission surface configured to receive a radiation flux and to emit secondary electrons due to the receipt of the radiation flux, the first radiation dose detector located upstream with respect to the second radiation dose detector viewed with respect to a direction of radiation transmission, and a meter, connected to each detector, to detect a current or voltage resulting from the secondary electron emission from the respective electron emission surface.

Lithographic apparatus, and device manufacturing method

The white light emitting diode comprising a light emitting component using a semiconductor as a light emitting layer and a phosphor which absorbs a part of light emitted by the light emitting component and emits light of wavelength different from that of the absorbed light, wherein the light emitting layer of the light emitting component is a nitride compound semiconductor and the phosphor contains garnet fluorescent material activated with cerium which contains at least one element selected from the group consisting of Y, Lu, Sc, La, Gd and Sm, and at least one element selected from the group consisting of Al, Ga and In and, and is subject to less deterioration of emission characteristic even when used with high luminance for a long period of time.

Light emitting device with blue light LED and phosphor components

An architectural approach for very-high-capacity wide-area optical networks is presented, and a proposed program of research to address key system and device issues is described. The network is based on dense multiwavelength technology and is scalable in terms of the number of networked users, the geographical range of coverage, and the aggregate network capacity. Of paramount importance to the achievement of scalability are the notions of wavelength reuse and wavelength translation. A distributed optical interconnect that is wavelength-selective and electronically controllable, permitting the same limited set of wavelengths to be reused among other access stations, is employed. By exercising the wavelength-selective switches, the wavelength-routed connectivity between stations can be reconfigured as needed. A multihop overlay network involving wavelength translation and self-routing fast packet switches permits full connectivity, if desired among the access stations at the individual virtual circuit level. Using just eight wavelengths, such a network could in principle interconnect a population of 100 million users over a nationwide geography with an expected delay equal to that of 12 hops. >

A scalable multiwavelength multihop optical network: a proposal for research on all-optical networks

A lighting device comprises a solid state light emitter, first and second electrodes connected to the emitter, an encapsulant region comprising a silicone compound and a supporting region. The encapsulant region extends to an external surface of the lighting device. At least a portion of the first electrode is surrounded by the supporting region. The encapsulant region and the supporting region together define an outer surface which substantially encompasses the emitter. A method of making a lighting device, comprises electrically connecting first and second electrodes to an emitter; inserting the emitter into mold cavity; inserting an encapsulant composition comprising a one silicone compound; and then inserting a second composition to substantially surround at least a portion of the first electrode.

Lighting device and method of making

A comparison is presented of the performance of amplitude-shift-keying (ASK), frequency-shift keying (FSK), and differential-phase-shift-keying (DPSK) lightwave systems which operate at 10 Gb/s with directly modulated 1550-nm distributed feedback (DFB) laser transmitters and conventional 1310-nm dispersion-optimized fiber. Computer modeling techniques were used to accurately simulate the amplitude modulation response and the frequency modulation response of DBF lasers. The system performance is evaluated from simulated eye patterns for both direct and heterodyne detection. With the narrow-optical spectral widths of these signal formats, fiber chromatic dispersion limits up to 70 km were obtained for transmission at 1550-nm using conventional 1310-nm optimized fiber. >

Performance of directly modulated DFB lasers in 10-Gb/s ASK, FSK, and DPSK lightwave systems

The frequency modulation (FM) and amplitude modulation (AM) responses of a 1.5- mu m distributed feedback (DFB) laser were measured to 15 GHz. At 9-mW output power, the magnitude of the FM response was flat out to 12 GHz, and there was a 15-25-ps delay between the FM and AM responses. Computer simulation techniques indicate that the measured FM response is adequate to produce good eye patterns for frequency-shift-keying modulation at data rates up to 20 Gb/s. The high-speed frequency-shift-keying modulation capability of this 1.5- mu m DFB laser was experimentally confirmed at 11 Gb/s. >

Ten-to-twenty gigabit-per-second modulation performance of 1.5- mu m distributed feedback lasers for frequency-shift-keying systems

Two multichannel 1.3-μ m lens integrated surface-emitting laser arrays for massive data links were fabricated. The basic structure of the lasers consists of a short InGaAlAs multiple-quantum-well distributed-feedback (DFB) active-stripe array monolithically integrated with both a 45° total reflection mirror and an aspheric collimation lens. One of them, a four-channel laser array based on this structure, exhibited clear 25-Gb/s eye openings up to 50°C over all four channels and achieved a total output of 100 Gb/s. The other laser, a multiple-wavelength array for wavelength-division-multiplexing applications, produces multiple-wavelength emission thanks to precisely modified DFB gratings by electron beam lithography. It exhibited nine-wavelength stable single-mode operation (side-mode suppression ratio >; 40 dB) between 1260 and 1290 nm at 3.7-nm intervals, and a clear 25-Gb/s eye opening for each wavelength. These two surface-emitting laser arrays have demonstrated their suitability for next-generation multichannel data links (including 100-Gb Ethernet and optical interconnects).

25-Gb/s Multichannel 1.3- $\mu$ m Surface-Emitting Lens-Integrated DFB Laser Arrays

A new structure for a 13 /spl mu/m-wave length beam-expander integrated ridge-waveguide laser is demonstrated that does not require a regrowth step A narrow beam divergence of 54/spl deg/ (lateral) and 189/spl deg/ (vertical) enables a laser diode to be coupled to a cleaved singlemode fibre with an efficiency as high as 33% with a 1 dB alignment tolerance of /spl plusmn/24 /spl mu/m laterally and +15 /spl mu/m vertically >

1.3 µm beam-expander integrated laser grown by single-step MOVPE

A compact parallel optical receiver consisting of a four-channel 25-Gb/s CMOS transimpedance-amplifier (TIA) array and a PIN-PD array for board-to-board optical interconnects was developed. Both arrays are directly mounted on a multi-layer ceramic package. The 25-Gb/s TIA array was fabricated by using 65-nm CMOS technology. To improve gain flatness and reduce inter-symbol interference caused by insertion loss, a gain-stage amplifier with flat frequency response and a 50-Ω output driver with an analogue equalizer were implemented in the TIA array. The TIA array achieves transimpedance gain of 69.8 dBΩ, bandwidth of 22.8 GHz, and gain flatness of ±2 dB after equalizing the effect of insertion losses at the input and output ports. A compact 100-Gb/s CMOS optical receiver is composed of a four-channel 25-Gb/s PIN-PD and the TIA array mounted on a 16-mm-square multi-layer low-temperature on-fired ceramic (LTCC) package. To alleviate the inner-channel crosstalk, the output signal lines from the PIN-PD array are connected to the TIA array through the coplanar lines, which are sandwiched by the upper and lower ground layers and the right-and-left ground lines. The optical receiver demonstrates negligible inter-channel crosstalk of less than -17 dB at operation frequency up to 25 GHz. Its measured sensitivity for a solitary signal input at 10-12 BER is -8.1 dBm, and its crosstalk between adjacent channels is 0.8 dB. Moreover, its power dissipation is only 3.0 mW/Gb/s at a data rate of 25 Gb/s, and its total power consumption (including that of the equalizer function) is low, i.e., 295 mW.

Shinji Tsuji

Papers

Performance of directly modulated DFB lasers in 10-Gb/s ASK, FSK, and DPSK lightwave systems

Ten-to-twenty gigabit-per-second modulation performance of 1.5- mu m distributed feedback lasers for frequency-shift-keying systems

25-Gb/s Multichannel 1.3- $\mu$ m Surface-Emitting Lens-Integrated DFB Laser Arrays

1.3 µm beam-expander integrated laser grown by single-step MOVPE

A Compact 4 $\, \times \,$ 25-Gb/s 3.0 mW/Gb/s CMOS-Based Optical Receiver for Board-to-Board Interconnects