Silica-based 8×8 optical matrix switch integrating newswitching units with large fabrication tolerance

An 8×8 optical matrix switch consisting of asymmetric Mach-Zehnder (MZ) interferometer switching units with a waveguide intersection was fabricated using silica-based planar lightwave circuits (PLC's) on a silicon substrate. This switching unit can realize a high extinction ratio and a wide operation wavelength range even if the coupling ratios of the directional couplers (DC's) consisting the switching unit, deviate greatly from the ideal value of 50%. A matrix switch with a DC-coupling ratio of 30% was fabricated to test the validity of the proposed geometry. The average insertion loss was 7.3 dB in the transverse electric (TE) mode and 7.5 dB in the transverse magnetic (TM) mode. The average extinction ratio was 31.2 dB in the TE mode and 31.3 dB in the TM mode. The wavelength range with an extinction ratio greater than 20 dB was over 100 nm     

Rearrangeable Nonblocking 8 × 8 Matrix Optical Switch Based on Silica Waveguide and Extended Banyan Network

Based on the crossbar network and the Banyan network (BN), a new rearrangeable nonblocking structure of extended Banyan network (EBN) was proposed for implementing an 8 times 8 optical matrix switch. The interconnection characteristics of the rearrangeable nonblocking EBN were studied, and the diagram of the logic program for driving the operation of switching units was provided. A silica waveguide 8 times 8 matrix optical switch was designed and fabricated according to the calculated results. The silica waveguide propagation loss of 0.1 dB/cm and waveguide-fiber coupling loss of 0.5 dB/facet were measured. With the fabricated 8 times 8 matrix optical switch, the insertion loss of 4.6 dB, the crosstalk of -38 dB, the polarization-dependent loss of 0.4 dB, the averaged switching power of 1.6 W, and the switching time of 1 ms were achieved. A basic agreement between experimental results and theoretical calculated values was achieved     

Silica-based 8×8 optical matrix switch module with hybridintegrated driving circuits and its system application

A compact, low-crosstalk 8×8 optical matrix switch module has been developed. A thermooptic switch chip and driving circuits with TTL interfaces are integrated on a 100-mm² ceramic substrate. It achieved a low insertion loss of 10.0 dB, a low crosstalk level of -25.9 dB, and had excellent stability in practical operation. A photonic intermodule connector for electronic switching systems in the near future is also demonstrated through the use of these optical switch modules     

High-extinction ratio and low-loss silica-based 8×8 strictlynonblocking thermooptic matrix switch

This paper describes a silica-based 8×8 strictly nonblocking thermooptic matrix switch with a high-extinction ratio and low loss. We realized this matrix switch by using a configuration which combines a double Mach-Zehnder interferometer (MZI) switching unit and an N×N matrix arrangement thus reducing the total waveguide length. The 8×8 matrix switch was fabricated on a 4-in wafer using planar lightwave circuit technology. We obtained an average extinction ratio of 60.3 dB and an average insertion loss of 5.1 dB. The operating wavelength bandwidth completely covers the gain band of practical erbium-doped fiber amplifiers (EDFAs)     

Polarization independent LiNbO3 8×8 matrix switch

A polarization-independent LiNbO₃ strictly blocking 8×8 matrix switch has been developed. A relatively low insertion loss, below 12 dB, has been obtained by a reduction in bending loss, using a wide bent waveguide width. The switch has less than -18.7-dB crosstalk and about 85-V switching voltage at any incident polarization with 1.3-μ wavelength light     

Multimode interference photonic switches (MIPS)

The switching characteristics of multimode interference photonic switches (MIPS) are analyzed by wide-angle finite difference beam propagation method (FD-BPM). As a result, it is found that the MIPS with a multimode interference (MMI) length of 599 μm can switch the output light polarization insensitively with a crosstalk of less than -20 dB for a wavelength range of 70 nm. These analyses show that the MIPS can also have a 3-dB coupler function. Experimentally, an InGaAsP/InP 1×2 MIPS with a thicker InP cladding layer was fabricated and exhibited switching operation with crosstalks of -8 dB and -10 dB at 0 and 20 mA current injections, respectively. For a 2×2 MIPS with a thinner InP cladding layer, better switching characteristics with a crosstalk of -13 dB and an extinction ratio of 17 dB were realized     

A 1×8 InP/InGaAsP optical matrix switch with low insertionloss and high crosstalk suppression

We present a current controlled passive 1×8 InP/InGaAsP optical matrix switch for routing applications at wavelength 1.55 μm. It is realized in a tree architecture and has integrated tapers for efficient fiber butt coupling. An AR coated device has average fiber-chip-fiber insertion losses of 6.8 and 6.3 dB for TE and TM polarizations, respectively. The homogeneity of the eight outputs is better than 0.3 dB in each polarization state. The crosstalk suppression is better than 19 dB. The performance of the device indicates that large InP-based switching matrices can be realized     

8×8 symmetric nonblocking integrated acoustooptic spaceswitch module on LiNbO3

An 8×8 symmetric nonblocking integrated acoustooptic space switch module has been realized on a Y-cut LiNbO₃ substrate, 1.0×10.0×37.0 mm in size. The switch module consists of a new hybrid beam expanding-collimating lens, a large aperture focusing lens, and a pair of four-element tilted surface acoustic wave (SAW) transducer arrays in a titanium-in-diffused channel-planar-channel composite waveguide. Experimental results of point-to-point nonblocking switching at the optical wavelength of 0.6328 μm, including an average crosstalk of -12.2 dB, optical switching efficiency of 25% at 125 mW RF drive power, carrier frequency increment of 13.5 MHz for switching between adjacent output channels and reconfiguration time of 0.4 μs have been obtained     

High-extinction ratio and low-loss silica-based 8×8thermooptic matrix switch

A high-extinction ratio and low-loss silica-based 8×8 thermooptic matrix switch is demonstrated. The 8×8 matrix switch is realized by using a double Mach-Zehnder interferometer switching unit and a matrix arrangement which reduces the total waveguide length. The average extinction ratio and the average insertion loss are 60.3 and 5.2 dB, respectively     

Performance of rearrangeable nonblocking 4×4 switch matriceson LiNbO3

The design, fabrication, and characterization of rearrangeable nonblocking 4×4 switch matrices and the development of a novel ITO (indium-tin-oxide)/Au multilayer electrode that leads to low switching voltages and low DC drift is reported. Results on electrode systems, insertion loss, crosstalk, tolerances in the coupling length, and stability obtained for eight fabricated matrices are given. In comparison to the SiO₂ buffer layers, a reduction in the switching voltage of a factor of 0.66 has been achieved. Insertion losses of fiber pigtailed modules are in the range between 4 and 7 dB. The crosstalk has still to be improved. The stability of the operating points of the switches has been analyzed, showing that the devices must be operated in closed dark housings with a passivation layer in order to avoid optical damage effects from ambient light and to protect them against physical and chemical influences     

Compact latching type PANDA fiber switch

A compact and low-polarization crosstalk 1×2 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 10⁴ switching operations     

New structure of silica-based planar lightwave circuits forlow-power thermooptic switch and its application to 8 × 8 opticalmatrix switch

We propose a novel structure that reduces the switching power of a silica-based thermooptic switch (TOSW). The structure consists of silicon trenches and heat insulating grooves, which are formed beneath and beside the arms of a Mach-Zehnder interferometer, respectively. We optimize the structure using the differential-element method (DEM) and fabricate a 2 × 2 TOSW with a switching power of only 90 mW, namely, 75% less than that of a conventional TOSW. We also obtain an insertion loss of about 1 dB and an extinction ratio of over 30 dB with a response time from 0% to 90% of 4.9 ms. We then use the structure to fabricate an 8 × 8 matrix switch and confirm a total power consumption of 1.4 W with an average insertion loss of 7.4 dB and an extinction ratio of 50.4 dB for 64 possible optical paths     

128 line photonic switching system using LiNbO3 switchmatrices and semiconductor traveling wave amplifiers

The possibility of a 128-line photonic space division switching system incorporating LiNbO₃ switch matrices and semiconductor traveling wave amplifiers (TWAs) is discussed. System design is considered in terms of the most suitable location for the TWA devices that gives the most practical power margin. Design requirements for a 128-line photonic switching system suitable for a small-sized private branch exchange requirement are presented along with experimental results. It has been shown that a five-stage switch cascade, suitable for such a high-capacity switching system with a power margin of greater than 5 dB in the highest switch loss situation is possible, using low-facet-reflection TWAs. Such TWA devices have been developed in the 1.3-μm wavelength region with maximum fiber-to-fiber gain values of 15 dB. With maximum gain-polarization dependencies of 3 dB, switch losses can be compensated even under TM mode operation     

Polarization-insensitive InP-based MQW digital optical switch

A polarization-insensitive InP-based p-i-n multiple-quantum-well switch is demonstrated for the first time. Polarization-insensitive switching and loss are achieved. Crosstalk and loss measurements across a wavelength range of 20 nm centered at 1.55 μm are reported. A crosstalk of better than -13 dB is achieved for both TE and TM polarizations across the 1.54-1.56-μm wavelength range with a switching voltage of -7 V. A low on-chip loss of less than 3 dB is achieved for both TE and TM across the above wavelength range, with a compact switch structure which is 3 mm long     

Prototype 32×32 optical switch matrix

A 32×32 optical switch matrix with a banyan network architecture is demonstrated using a Ti:LiNbO₃ waveguide. The switching voltage was 24 V and extinction ratio averaged -18 dB. The prototype device showed path dependent insertion loss deviation of 10 dB. The device can be used as a building block for many functional optical switch matrices     

Tunable Mach-Zehnder polarization splitter using height-tapered Y-branches

A tunable TE/TM polarization splitter, based on a Mach-Zehnder interferometer with an electrooptic switch, is demonstrated in GaAs-AlGaAs. Symmetric and asymmetric Y-branches employing height-tapered waveguides are used to achieve power splitting and mode sorting, respectively, in the interferometer. The device has an extinction ratio of /spl sim/20 dB and an excess loss less than 1.5 dB for both TE and TM polarized light. The device can be reconfigured by tuning the switching voltage for operation at both 1.3- and 1.55-pm wavelengths.     

A high-speed 4×4 Ti:LiNbO3 integrated optic switchat 1.5 μm

The operation of a fully packaged and pigtailed polarization dependent Ti:LiNbO₃ 4×4 integrated optic switch with an operating wavelength of 1.5 μm is demonstrated. The switching matrix is fast, with a measured 3-dB small-signal bandwidth greater than 1 GHz. Unwanted cross modulation between channels due to coupling between switching elements was measured and found to be less than -20 dB of the signal strength. The switch is composed of balanced bridge switching elements having a 17-V switching voltage, an 18 dB extinction ratio, and an excess optical loss of 0.6 dB     

Client-configurable eight-channel optical add/drop multiplexerusing micromachining technology

A client-configurable optical add/drop multiplexer (OADM) is demonstrated using a micromachined 8×6 matrix switch. The matrix switch can be configured to add/drop any of the eight input channels from/to any of the six add/drop ports. For the switching fabric, the insertion loss is 2~3 dB for the dropped channels and 8~9 dB for the added channels by using the backsides of the micromirror switches. The switching extinction ratio is over 40 dB, the crosstalk between channels is less than -40 dB, and they are equipment-limited in this experiment     

SiGe/Si bifurcation optical active switch based on plasmadispersion effect

Based on the plasma dispersion effect of Si_1-xGe_x , 2×2 bifurcation optical active switches have been fabricated, in which the Si_1-xGe_x was grown by molecular beam epitaxy. At a 36 mA injection current, the device reaches maximum optical switching. The crosstalk is less than -11 dB and the insertion loss is 3.8 dB. The measured response time is <100 ns     

2×2 optical waveguide switch with bow-tie electrode based oncarrier-injection total internal reflection in SiGe alloy

Based on the total internal reflection and the plasma dispersion effect of SiGe alloy, a 2×2 intersectional rib optical waveguide switch with bow-tie electrode has been proposed and fabricated for the wavelength of 1.3-μm operation. The thickness of the SiGe layer is 2.6 μm and the width is 9 μm. The branch angle of the switch is 2° and the bow-tie angle is 1.5°. The on-state crosstalk is -19.6 dB, the off-state extinction ratio is 38.5 dB and the off-state insertion loss is less than 1.70 dB. The switching time is about 180 ns