Fabrication of semiconductor optical switch module using laser welding technique

The 4/spl times/4, 1/spl times/2, and 1/spl times/4 semiconductor optic-switch modules for 1550 nm optical communication systems were fabricated by using the laser welding technique based on the 30-pin butterfly package. For better coupling efficiency between a switch chip and an optical fiber, tapered fibers of 10-15 /spl mu/m lens radius were used to provide the coupling efficiency up to 60%. The lens to lens distance of the assembled tapered fiber array was controlled within /spl plusmn/1.0 /spl mu/m. A laser hammering technique was introduced to adjust the radial shift, which was critical to obtain comparable optical coupling efficiencies from all the channels at the same time. The fabricated optical switch modules showed good thermal stability, with less than 5% degradation after a 200 thermal cycling. The transmission characteristics of the 4/spl times/4 switch module showed good sensitivities, providing error free transmissions below -30 dBm for all the switching paths. The dynamic ranges for the 4/spl times/4 and 1/spl times/2 switch modules were about 8 dB for a 3 dB penalty and about 17 dB for a 2 dB penalty, respectively.     

A three-dimensional MEMS optical switching module having 100 input and 100 output ports

This paper describes an optical switching module based on microelectromechanical systems (MEMS) two-axis tilt mirror arrays and low-cost highly accurate free-space optics. The MEMS mirror arrays are integrated on single-crystal silicon wafers and provide reliable switching operation at a low driving voltage. The free-space optics consists of two-dimensional optical fiber and microlens arrays based on low-cost and highly accurate polymer-based components. They provide a compact switching module (approximately 80/spl times/60/spl times/35 mm [170 cc]) and are assembled passively by using dowel pins. A prototype switch module with 100-ch optical fiber I/O has a low coupling loss of 4.0 dB, a low crosstalk within -60 dB, and switching time of 3 ms.     

Plug-in type 1.3-/spl mu/m fiber amplifier module for rack-mounted shelves

We have successfully developed a plug-in type PDFA module for rack mounted shelves which is assembled on a printed-board. In this module, we use a newly developed Pr/sup 3+/-doped high-NA PbF/sub 2//InF/sub 3/-based fluoride fiber and wavelength stabilized 1.017-/spl mu/m laser diodes (LDs). We have obtained a small-signal gain of 24 dB and a noise figure of 6.6 dB at 1.30 /spl mu/m with an LD drive current of 240 mA/spl times/2. We achieved an output power of 10 dBm with a signal input power of 0 dBm. The total power consumption of this module, including that of a Peltier cooler, was 3.5 W when the LD drive current was 240 mA/spl times/2.     

Low-loss polarization-insensitive InP-InGaAsP optical space switches for fiber optical communication

High-performance InP-InGaAsP optical space switches are reported, which in monolithic four switch arrangements reach fiber-to-fiber losses as low as 5 dB. Polarization insensitivity is within /spl plusmn/0.5 dB. On-off ratios throughout the 1.53-1.56 /spl mu/m wavelength range exceed 15 dB. Switch rearrangement times are below 200 ps.     

Multimode optical demultiplexer for DWDM with liquid crystal enabled functionalities

We have developed a liquid-crystal-based multimode optical demultiplexer (DEMUX) with additional functionalities such as switching and power equalization. Demultiplexing 16-channel 100-GHz-spaced signals into a 62.5-/spl mu/m multimode-fiber array is demonstrated. The central wavelength of each channel is designed according to the International Telecommunication Union grid. Adjacent channel crosstalk is less than -30 dB. The average 1and 3-dB passbands of the DEMUX are 12.5 and 22.5 GHz, respectively. A maximum extinction ratio of 16.2 dB is achieved. Different channels can be switched with rise and fall times of /spl sim/10 and /spl sim/70 ms, respectively. The outputs of the channels are equalized to -65 dBm. The variation between different channels reduced from /spl sim/10 dB to less than 0.5 dB.     

2/spl times/4 optical add-drop module with no difference in propagation length

We developed a micromachined X-type 2/spl times/4 optical add-drop module (OADM) featuring no difference in propagation length. Four pairs of lensed fibers are aligned in "X" position, and four micromirrors are located between the pairs of optical fibers. The OADM was fabricated utilizing a silicon-on-insulator process. Electrostatic comb actuators can be driven up to 90 /spl mu/m to change the light path within 1 ms. The insertion loss and the on-off ratio were less than 3 and 70 dB, respectively. The loss uniformity in every channel was 1.5 dB.     

Germania-based core optical fibers

Germania-glass-based core silica glass cladding single-mode fibers (/spl Delta/n up to 0.143) with a minimum loss of 20 dB/km at 1.9 /spl mu/m were fabricated by the modified chemical vapor deposition (MCVD) method. The fibers exhibit strong photorefractivity with the type-IIa-induced refractive-index modulation of 2/spl times/10/sup -3/. The Raman gain of 300 to 59 dB/(km/spl middot/W) was determined at 1.07 to 1.6 /spl mu/m, respectively, in a 75 mol.% GeO/sub 2/ core fiber. Only 3 m of such fibers are enough for the creation of a 10-W Raman laser at 1.12 /spl mu/m with a 13-W pump at 1.07 /spl mu/m. Raman generation in optical fiber at a wavelength of 2.2 /spl mu/m was obtained for the first time.     

Adaptive antenna receiver module for WLAN at C-band with low-power consumption

A low-power consuming adaptive antenna receiver module at C-band for 802.11a and HIPERLAN is presented. The highly integrated GaAs microwave monolithic integrated circuit consists of low noise amplifiers, calibration switches and a vector modulator with 360/spl deg/ phase control and over 15 dB gain control. At 5.2 GHz, the module has a maximum gain of 12.5 dB, a noise figure of 2.7 dB, and a 1 dB output compression point of -7 dBm. The module draws only 2.3 mA up to 3.5 mA from a 2.7 V supply. Chip size is 1.9 mm /spl times/ 1.6 mm.     

Compact polarization-insensitive InGaAsP-InP 2 /spl times/ 2 optical switch

We demonstrate a simple, compact, high-contrast ratio, and low-loss polarization-insensitive InGaAsP-InP 2 /spl times/ 2 optical switch with an operational wavelength range from 1520 to 1580 nm. The switch is 1.3 mm long by 160 /spl mu/m wide. The on-off contrast ratio is within (21/spl plusmn/2) dB over the temperature range from 16/spl deg/C to 64/spl deg/C, the polarization sensitivity is <2 dB, and the propagation loss is (3/spl plusmn/2) dB in both the ON and OFF states, making it potentially useful for optical cross-connects, delay lines, and add-drop multiplexers.     

Integrated circuits for a 200 Mbit/s fiber-optic link

A set of three bipolar integrated circuits for a new fiber-optic link is described. The link operates at data rates of 5-200 Mb/s NRZ. The optical transmitter and receiver modules are compact and fit into standard 16-pin dual-in-line sockets. The power consumption of the transmitter module is 530 mW and the receiver module dissipates 310 mW. The optical loss budget is 20 dB, which is sufficient for link lengths of up to 5 or 6 km. The circuits have been designed in a 3-/spl mu/m bipolar process. The chip sizes are 2 mm/spl times/1.75 mm each.     

A single-chip CMOS optical microspectrometer with light-to-frequency converter and bus interface

A single-chip CMOS optical microspectrometer containing an array of 16 addressable Fabry-Perot etalons (each one with a different resonance cavity length), photodetectors, and circuits for readout, multiplexing, and driving a serial bus interface has been fabricated in a standard 1.6 /spl mu/m CMOS technology (chip area 3.9 /spl times/ 4.2 mm/sup 2/). The result is a chip that can operate using only four external connections (including V/sub dd/ and V/sub ss/) covering the optical range of 380-500 nm with full-width half-maximum (FWHM) = 18 nm. Frequency output and serial bus interface allow easy multisensor and multichip interfacing using a microcontroller or a personal computer. Power consumption is 1250 /spl mu/W for a clock frequency of 1 MHz.     

Optoelectromechanical switch array with passively aligned free-space optical components

An all-optical switch array with micro mirrors driven by electrostatic micro motors has been developed in a LIGA-technique. The system has been designed for single mode application at the telecommunication wavelength of 1.55 /spl mu/m. All fixed optical components are passively aligned inside a LIGA-structured micro optical bench. The signals are detoured inside the optical bench by means of micro mirrors, which are attached to micro wobble motors. In order to avoid angular displacements of the deflected light beams double mirrors are used. First, prototypes with 2 input and output ports have been realized. Two of these 2 /spl times/ 2 switch matrices have been integrated on a 10 /spl times/ 10 mm/sup 2/ ceramic substrate with six micro motors of 1.7 mm diameter. Switching times down to 30 ms have been achieved. The crosstalk between different channels is 90 dB. The insertion loss with passive alignment of the optical elements yielded 3 dB with a repeatability better than /spl plusmn/0.3 dB.     

Planar-integrated free-space optical fan-out module for MT-connected fiber ribbons

This paper reports on the design, the fabrication, and the testing of a compact planar-integrated free-space optical 1 /spl rarr/ 4 fan-out module for fiber ribbons with multifiber-terminated connectors. It supports 12 parallel optical channels and consists of a cascade of basic cells with 1 /spl rarr/ 2 fan-out. The module was implemented with surface-relief diffractive-phase elements; design and fabrication of the optical system were optimized for low loss by various measures such as the use of dielectric and silver reflective coatings. In experimental tests, a coupling efficiency of -11.4 dB per fan-out channel was obtained.     

A 1.8-V 10-Gb/s fully integrated CMOS optical receiver analog front-end

A fully integrated 10-Gb/s optical receiver analog front-end (AFE) design that includes a transimpedance amplifier (TIA) and a limiting amplifier (LA) is demonstrated to require less chip area and is suitable for both low-cost and low-voltage applications. The AFE is fabricated using a 0.18-/spl mu/m CMOS technology. The tiny photo current received by the receiver AFE is amplified to a differential voltage swing of 400 mV/sub (pp)/. In order to avoid off-chip noise interference, the TIA and LA are dc-coupled on the chip instead of ac-coupled though a large external capacitor. The receiver front-end provides a conversion gain of up to 87 dB/spl Omega/ and -3dB bandwidth of 7.6 GHz. The measured sensitivity of the optical receiver is -12dBm at a bit-error rate of 10/sup -12/ with a 2/sup 31/-1 pseudorandom test pattern. Three-dimensional symmetric transformers are utilized in the AFE design for bandwidth enhancement. Operating under a 1.8-V supply, the power dissipation is 210 mW, and the chip size is 1028 /spl mu/m/spl times/1796 /spl mu/m.     

8/spl times/8 optical switch matrix using generalized Mach-Zehnder interferometers

We report an 8/spl times/8 strictly nonblocking optical cross connect (OXC) using multimode imaging (MMI)-based generalized Mach-Zehnder (MZ) interferometers realized in the silica-on-silicon planar waveguide system. Employing a router-selector architecture, this MMI-MZ OXC design results in a significantly smaller device than conventional directional-coupler based implementations. An average insertion loss of 6 dB and crosstalk of -34 dB, is demonstrated for the 8/spl times/8 OXC.     

A compact LTCC-based Ku-band transmitter module

Presents design, implementation, and measurement of a three-dimensional (3-D)-deployed RF front-end system-on-package (SOP) in a standard multi-layer low temperature co-fired ceramic (LTCC) technology. A compact 14 GHz GaAs MESFET-based transmitter module integrated with an embedded bandpass filter was built on LTCC 951AT tapes. The up-converter MMIC integrated with a voltage controlled oscillator (VCO) exhibits a measured up-conversion gain of 15 dB and an IIP3 of 15 dBm, while the power amplifier (PA) MMIC shows a measured gain of 31 dB and a 1-dB compression output power of 26 dBm at 14 GHz. Both MMICs were integrated on a compact LTCC module where an embedded front-end band pass filter (BPF) with a measured insertion loss of 3 dB at 14.25 GHz was integrated. The transmitter module is compact in size (400 /spl times/ 310 /spl times/ 35.2 mil/sup 3/), however it demonstrated an overall up-conversion gain of 41 dB, and available data rate of 32 Mbps with adjacent channel power ratio (ACPR) of 42 dB. These results suggest the feasibility of building highly SOP integrated RF front ends for microwave and millimeter wave applications.     

Carrier synchronization for 3- and 4-bit-per-symbol optical transmission

We investigate carrier synchronization for coherent detection of optical signals encoding 3 and 4 bits/symbol. We consider the effects of laser phase noise and of additive white Gaussian noise (AWGN), which can arise from local oscillator (LO) shot noise or LO-spontaneous beat noise. We identify 8- and 16-ary quadrature amplitude modulation (QAM) schemes that perform well when the receiver phase-locked loop (PLL) tracks the instantaneous signal phase with moderate phase error. We propose implementations of 8- and 16-QAM transmitters using Mach-Zehnder (MZ) modulators. We outline a numerical method for computing the bit error rate (BER) of 8- and 16-QAM in the presence of AWGN and phase error. It is found that these schemes can tolerate phase-error standard deviations of 2.48/spl deg/ and 1.24/spl deg/, respectively, for a power penalty of 0.5 dB at a BER of 10/sup -9/. We propose a suitable PLL design and analyze its performance, taking account of laser phase noise, AWGN, and propagation delay within the PLL. Our analysis shows that the phase error depends on the constellation penalty, which is the mean power of constellation symbols times the mean inverse power. We establish a procedure for finding the optimal PLL natural frequency, and determine tolerable laser linewidths and PLL propagation delays. For zero propagation delay, 8- and 16-QAM can tolerate linewidth-to-bit-rate ratios of 1.8/spl times/10/sup -5/ and 1.4/spl times/10/sup -6/, respectively, assuming a total penalty of 1.0 dB.     

Active vertical-coupler-based optical crosspoint switch matrix for optical packet-switching applications

Packet-switching characteristics are optimized across an integrated 4 /spl times/ 4 optical crosspoint switch matrix consisting of active vertical-coupler-based switch cells. Optical gain difference between the shortest and the longest paths less than 3 dB is demonstrated. Bit error rate (BER) and power penalty measurements during packet routing have also been carried out over the entire 4 /spl times/ 4 matrix. At a 10-Gb/s packet data rate, a less than 1-dB power penalty is observed across the switch matrix, and the possibility for error-free packet routing is demonstrated with no BER floor observed.     

High-density digital free-space photonic switches using micro-beam optical interconnections

We describe a compact free-space photonic-switching module that uses micro-beam optical interconnections based on stacked planar optics and exciton absorption reflection switch (EARS) arrays. The switching module has two-dimensional fiber array pigtails and a two-stage, 16-input, 16-output structure (four sets of 4/spl times/4 switches). The microbeam optical interconnections can provide a compact switching module (approximately 30/spl times/90/spl times/22 mm [60 cc]). A relay lens array inserted between stages eliminates beam spreading in the switch and decreases the coupling loss and crosstalk of interconnections. Two-stage switching at a data transmission rate of 4 Mbit/s is demonstrated.