Permanent attachment of single-mode fiber arrays to waveguides

We report on coupling arrays of SM fibers in siliconV- grooves to waveguides. Arrays with up to 12 fibers have been permanently attached to waveguides with an average excess loss of 0.3 dB per interface. We discuss a subtle, heretofore unreported effect of polarization on fiber-waveguide insertion loss and we describe the first measurements of waveguide-mode position as a function of polarization. In general, the modes of a Ti:LiNbO3waveguide peak at different positions. This results in different optimum positions for coupling and thus leads to an unavoidable excess loss when attaching fibers. For low-loss waveguides, we predict a minimum excess loss of 0.25 dB per interface.     

1.5%-/spl Delta/ athermal arrayed-waveguide grating multi/demultiplexer with very low loss groove design

We describe a compact 1.5%-/spl Delta/ athermal silica-based 100-GHz-spacing 16-channel arrayed-waveguide grating (AWG) multi/demultiplexer with a modified groove design for a very low excess loss. We propose new approaches for modifying the shape of the grooves and the arrayed waveguides and optimize the shape modifications for 1.5%-/spl Delta/ waveguides. By employing this modified groove design, we greatly reduced the groove excess loss from 1.9 to 0.4 dB in the 1.5%-/spl Delta/ athermal AWG.     

Low-loss TM-pass polariser fabricated by proton exchange for z-cut ti:LiNbO3 waveguides

We fabricated a low-loss TM-pass polariser at ? = 1.32 ?m integrated with low-loss titanium waveguides in Z-cut LiNbO3. The polariser, fabricated by proton exchange, had an excess insertion loss of 0.3 dB and a polarisation extinction ratio of > 40dB.     

New low-loss broadband SAW filter using unidirectional IDTs with U-shaped MSCs

A new low-loss broadband SAW filter is presented. A new configuration using one pair of electrically connected IDTs with an optimum number of fingers, as well as unidirectional IDTs with U-shaped MSCs, is described. Experimental results with bandwidth as wide as 10% and loss as low as 3 dB are achieved. Very accurate computer-aided design of a low-loss filter with MSCs is obtained.     

Topology optimised broadband photonic crystal Y-splitter

A planar photonic crystal waveguide Y-splitter that exhibits large-bandwidth low-loss 3 dB splitting for TE-polarised light has been fabricated in silicon-on-insulator material. The high performance is achieved by utilising topology optimisation to design the Y-junction and by using topology optimised low-loss 60/spl deg/ bends. The average excess loss of the entire component is found to be 0.44/spl plusmn/0.29 dB for a 100 nm bandwidth, and the excess loss due to the Y-junction is found to be 0.34/spl plusmn/0.30 dB in a 175 nm bandwidth.     

True-time-delay element in lossy environment using EO waveguides

We investigate a photonic true time delay element in a lossy environment using electrooptic waveguides. Its principle is based on the ring resonator and the all-pass filter. In the lossy environment, it is known that the insertion loss depends on the delay time when using the conventional ring resonator. We add a by-pass waveguide to the ring resonator in order to compensate the resonant-dependent loss. As a result, we have a voltage-controlled photonic true time delay element with its insertion loss independent of the delay time.     

High-temperature superconducting delay lines and filters onsapphire and thinned LaAlO3 substrates

The very low microwave surface resistance of high-temperature-superconductor (HTS) thin films allows the realization of microwave devices with performance superior to those made by conventional technology. Superconducting delay lines, for example, have very low propagation loss and dispersion. Long, low-loss, superconducting delay lines on both thinned LaAlO₃ and sapphire substrates are presented. Delay lines with 27- and 44-ns delay have been made, for the first time, on 5-cm-diameter 254- and 127-μm-thick LaAlO₃ substrates, respectively. The insertion losses at 77 K and 6 GHz are 6 and 16 dB, respectively. Delay lines with 9-ns delay have, for the first time, been produced on M-plane sapphire substrates and demonstrate, at 77 K, an insertion loss of 1.0 dB at 6 GHz. A 2.5%-bandwidth 10 GHz four pole edge-coupled bandpass filter on M-plane sapphire substrates is also reported. The filter has minimum insertion loss of less than 0.5 dB at 9.75 GHz and 71 K     

Low-loss bandpass filter using higher mode strip line for millimetre-wave integrated circuits

A technique to construct a low-loss printed bandpass filter was demonstrated by using a higher mode strip line at 30 GHz. A three-pole, 0.1 dB Chebyshev ripple bandpass filter with a 2% relative bandwidth was designed and fabricated. The insertion loss was found to be 0.7 dB.     

Waveguide Interconnection in Silica-Based Planar Lightwave Circuit Using Femtosecond Laser

The interconnection of waveguides inside a silica- based planar lightwave circuit (PLC) is demonstrated both two- and three-dimensionally by using a femtosecond laser. The waveguides written with a femtosecond laser can be successfully connected to waveguides inside a PLC with low loss. Unlike previous work on the direct writing of 2-D and 3-D waveguides in bulk glass, the waveguide must be written a few tens of micrometers beneath the surface of a PLC composed of multilayers of different glasses. To realize a low-loss waveguide, we studied the sensitivity difference for femtosecond pulses in each layer in detail and developed a multiple-scanning technique with a femtosecond laser for writing waveguides. In addition, we investigated a mode-field (MF) diameter control technique to allow us to achieve the low-loss interconnection of PLC and written waveguides. We also studied particular problems caused by nonlinear optical effects, such as the positional displacement of written waveguides from the focal point. As a result, we achieved a low-loss waveguide with almost the same MF diameter as a PLC waveguide and performed the first demonstration of interconnection between PLC waveguides. The excess losses at 1550 nm were 1.4 and 2.3 dB for 2-D and 3-D interconnection, respectively.      

Groove guide as a low-loss transmission system for short millimetric waves

Groove guide promises low-loss transmission at short millimetric wavelengths, coupled with simple construction and convenient dimensions. Even though the guide is of overmoded dimensions, the groove acts as a higher-order-mode filter. Approximate analytical solutions are shown to be adequate to give sufficiently accurate propagation characteristics. Higher-mode suppression is investigated and shown to be effective at 8 mm wavelength.     

16-band integrated dynamic gain equalization filter with less than2.8-dB insertion loss

We demonstrate a low-loss 16-band dynamic gain equalization filter consisting of two perfectly sampled waveguide grating routers (WGRs) and an array of thermooptic attenuators. This integrated silica waveguide filter has <2.8-dB fiber-to-fiber insertion loss, <0.2-dB polarization-dependent loss at minimum attenuation and <0.7-dB at 10-dB extra attenuation, and <5.0-W electrical power consumption over the C-band. We also demonstrate a new technique for reducing the loss of WGRs     

Miniaturized SAW devices for radio communication transceivers

Various applications of surface-acoustic-wave (SAW) technologies are investigated in which the use of SAW devices would result in reduced volume and weight for VHF/UHF radio communication transceivers. Attention is given to improved insertion loss and power requirements reported for SAW filters. In particular, by analyzing the loss mechanisms of a previously developed high-performance SAW filter for mobile telephones, a new extremely low-loss SAW filter (loss of as low as 1.2-2.0 dB at 600 MHz) has been developed. The results of fundamental experiments for a SAW antenna duplexer using this new SAW filter as the transmitter filter with a semicoaxial filter as the receiver filter at 800 MHz are presented     

A Comb-Line Elliptic Filter

The design of a new type of elliptic filter, particularly suitable for narrow-band low-loss applications at VHF and UHF, is presented. The filter is derived from a lumped-element bandpass prototype by replacing the lumped inductors, which are normally the main contributory factors to the loss, by a comparatively low-loss distributed network. The latter consists of an n-wire digital line short-circuited at one end, the length of which is i/8 or less. An experimental elliptic filter of fifth order was constructed at 136.6 MHz with a pass bandwidth of 5 MHz, having 60-dB points at /spl plusmn/ 7 MHz from midband. The measured insertion loss of 1.1 dB is lower than that of a comparable lumped-element filter by a factor of at least 3,5:1. It compares favorably also with a comb-line filter, both in terms of loss and physical size.     

Continuous-time delta-sigma modulator using vector filter in feedback path to reduce effect of clock jitter and excess loop delay

In this paper, we propose a novel delta-sigma modulator (DSM) that reduces the effects of clock jitter and excess loop delay by using a vector filter in the feedback path. The vector filter divides the input signal into a high-frequency part and a low-frequency part. The low-pass signal is placed in the path to the first-stage digital-to-analog converter for reducing the effects of the clock jitter, and the high-pass signal is placed in the feedback path to the last integrator in order to compensate for the excess loop delay. The DSM using the vector filter in the feedback path (DSM-VF) is verified using MATLAB/Simulink. Further, a clock jitter (0.1 %) in DSM-VF leads to an improvement in the signal-to-noise-ratio (SNR) to 22.5 dB as compared to the SNR of a conventional CTDSM. Moreover, the SNR deterioration caused by the excess loop delay is improved.     

Energy-trapped shallow bulk acoustic waves

A low-loss high-sidelobe-rejection shallow bulk acoustic filter has been constructed. The delay line consisted of apodised and finger-withdrawal-weighted transducers as well as a metallic energy-trapping grating. Experimental results are given and discussed.     

Low-loss 4 × 4 optical matrix switch for fibre-optic communication

A low-loss and high-repeatability 4 × 4 optical matrix switch fabricated by using rhombic glass-block switch elements is described. The maximum loss was 1.3 dB and the crosstalk was less than ?55 dB, with a switching delay of less than 18 ms.     

A Fully Embedded 60-GHz Novel BPF for LTCC System-in-Package Applications

In this paper, a novel LTCC stripline (SL) 60-GHz band-pass filter (BPF) composed of transitions to coplanar waveguide (CPW) pads for monolithic microwave integrated circuit integration is presented. For low-loss interconnection with active devices, a CPW-to-SL vertical via transition integrating air cavities and a CPW-to-CPW planar transition using internal ground planes are proposed and implemented. The fabricated transition shows an insertion loss of 1.6 dB and a reflection loss below -20 dB at the passband of the filter. The implemented SL BPF using dual-mode patch resonators shows a center frequency of 60.4 GHz, 3.5 % bandwidth, and reflection losses below -15 dB at the passband. Excluding the insertion loss of the transitions, the filter insertion loss reveals 4.0 dB     

W-band micromachined circuit combining networks

In circuit-combining networks, low-loss interconnecting transmission lines are pivotal in reducing excess loss. Micromachined finite ground coplanar waveguides are used in this study as low-loss interconnects showing significant improvements in line loss while maintaining 50-Ω characteristic impedance. Wilkinson power dividers, reactive tee junctions, and right-angle bends are combined with micromachined interconnects in 1:2, 1:4, and 1:8 power-dividing networks and show measured loss reduction of 0.3-1.0 dB depending on circuit type and size from 85 to 95 GHz     

Low-loss Y-coupler for multimode single fibres

A technique for making low-loss 3dB Y-couplers in multimode single fibres was developed and evaluated. The couplers were obtained by the fusion of two optical fibres by means of a neated Kantal wire. A set of fifty samples using a Pilkington step-index fibre showed an average excess insertion loss of about 0.7dB.     

Compact mode expanded lasers using resonant coupling between a1.55-μm InGaAsP tapered active region and an underlying couplingwaveguide

We demonstrate a novel expanded mode laser for enhanced laser-fiber coupling based on resonant coupling between a tapered active waveguide and an underlying coupling waveguide. This device was grown in a single standard epitaxial growth and was processed using conventional fabrication techniques, thus making it attractive for low-cost manufacturing. The total taper length required for mode transformation was 200 μm and the excess transformation loss was 0.6 dB indicating the compact, low-loss mode transformation. Far-field divergence angles (13°×24°) and improved coupling to cleaved single-mode fibers (3.8-dB coupling loss), were achieved