Polarization mode converter with polyimide half waveplate insilica-based planar lightwave circuits

A TE/TM polarization mode converter, with an excess loss of 0.26 dB, is constructed by inserting a polyimide half waveplate into a groove formed in a silica-based single mode waveguide. The polarization dependence of an arrayed-waveguide grating multiplexer is completely eliminated with this mode converter     

Feed-forward continuous and complete polarization control with a PLZT rotatable-variable waveplate and inline polarimeter

A Pb/sub 1-x/La/sub x/(Zr/sub y/Ti/sub z/)/sub 1-x/4/O/sub 3/ (PLZT) electrooptic ceramic variable-rotatable waveplate and a compact inline polarimeter have been used to develop a fast feed-forward-controlled module for the continuous and complete conversion of polarization. This requires the control of only two parameters: the direction /spl theta/ and strength of the applied voltage V/sub 0/. Feed-forward control speed is fast, taking only 24 /spl mu/s. The chip plates were made by cutting T-shaped trenches into the four sides of a 500/spl times/400/spl times/300-/spl mu/m/sup 3/ PLZT chip and coating the trenches with electrodes. The PLZT waveplate is inserted into a 330-/spl mu/m gap between thermally expanded core fibers. The input polarization states are monitored by a newly developed compact and fast inline polarimeter, which is placed in front of the polarization controller. The optimum /spl theta/ and V/sub 0/ values for the required conversion are calculated by a computer, and the corresponding voltages are then applied to PLZT waveplate.     

Highly stable optical add/drop multiplexer using polarization beam splitters and fiber Bragg gratings

We demonstrate a novel wavelength-division add/drop multiplexer employing fiber Bragg gratings and polarization beam splitters. The multiplexer is easy to fabricate without any special technique such as UV trimming, and yet shows very stable performance with less than 0.3-dB crosstalk power penalty in a 0.8-nm-spaced, 2.5-Gb/s-per-channel wavelength-division multiplexing (WDM) transmission system.     

On polarization sensitivity of all-optical label swapping using synchronous phase modulation

Polarization sensitivity degrades the performance of many optical devices in optical packet switched networks. We investigate the polarization sensitivity for all-optical label swapping for the first time. We propose and demonstrate a polarization-insensitive phase modulator for all-optical label swapping. The polarization sensitivity of the power penalty for the label swapping is less than 0.3 dB.     

Elimination of PD-/spl lambda/ at all output ports of silica-based AWG

It is shown that the polarisation dependent wavelength shift (PD-/spl lambda/) of a silica-based arrayed waveguide grating (AWG) is proportional to its output port location as a result of the birefringence in a slab waveguide. This PD-/spl lambda/ was eliminated to less than 0.01 nm by inserting a half waveplate across the slab waveguide.     

Elimination of acoustic sensitivity in nonlinear optical loopmirrors

Acoustic disturbance is known to give rise to bit error rate (BER) floor when using the nonlinear optical loop mirror as a switch. Here, the acoustically induced penalty is investigated and >30 dB improvement in the acceptable acoustic sound pressure (50 Hz-5 kHz) is achieved by rewinding the loop fiber symmetrically. Only 1.5 dB sensitivity penalty was observed at a sound pressure of 110 dBA when using a nonlinear optical loop mirror (NOLM) containing 3.9 km of dispersion shifted fiber     

High-speed analogue multiplexer using s.a.w. technology

A new type of high-speed analogue multiplexer is described that utilises surface-acoustic-wave (s.a.w.) technology. The device operation is based upon the conversion of P parallel analogue control inputs into a serial-output amplitude-modulated pulse train superimposed on a v.h.f. carrier. Experimental results are presented for a 10-channel prototype device with a sampling rate near 1 MHz and a modulation dynamic range exceeding 50 dB. The feasibility of achieving 100-channel operation at sampling rates up to 100 MHz is discussed.     

A key component in optical systems: the silica-based arrayed waveguide grating (de)multiplexer. Overview and perspectives

In the ten past years, the telecommunication industry has experienced an unprecedented growth rate. To follow the exponential Bandwidth demand, new transmission technologies have emerged. Amongst them, we find Wavelength Division Multiplexing (WDM) technology. Its appearance coinciding with the emergence of key optical functions. This paper addresses one of these key optical functions, today an absolute must: wavelength demultiplexing. This function can be realized thanks to a demultiplexer, also named AWG, the acronym for Arrayed Waveguide Gratings. It took only ten years to transform the first research experiments into real commercial products: demultiplexers using a silica on silicon planar platform. This platform allowed yesterday the realization of demultiplexer AWG-products, managing high channels count at a relatively low cost, today this same platform allows the integration of complex optical functions with a more drastic cost reduction. As for tomorrow, transmission systems will continue to require new signal processing functions to permit high bit rate transmission. Once again, the AWG can play a key role.     

Bending loss reduction in silica-based waveguides by using lateraloffsets

The excess loss that occurs in waveguide bends can be minimized by offsetting the connecting waveguides so as to reduce the transition loss at the junctions. Such bends were investigated in detail by employing the beam propagation method (BPM) and it was found that they can be optimized with respect to overall loss. In the addition, the S-shaped waveguides and directional couplers with offset junctions were fabricated based on silica-based planar lightwave circuits (PLC) on silicon substrates. The measured insertion losses of these S-shaped waveguides and directional couplers, which are in good agreement with the calculated results, are the lowest thus far reported     

Gain distribution measurement of an erbium-doped silica-based waveguide amplifier using a complex OLCR

We have measured the gain distributions of a 38-cm-long erbium-doped silica-based waveguide amplifier with different pump powers by using a complex optical low coherence reflectometer. The spatial resolution is /spl sim/5 mm and the noise level is /spl plusmn/1 dB. The measured distributions agree well with those derived from rate equations. We can estimate such amplifier parameters as the stimulated emission coefficient and the optimum waveguide length enabling us to achieve the maximum gain for any pump power.     

Angle estimation using a polarization sensitive array

In a previous work (see ibid., vol.39, no.9, p.1376-83, 1991) the authors described how the ESPRIT algorithm may be used to estimate both the arrival directions and the polarizations of incoming plane waves with a uniform linear array of crossed dipoles. An alternative approach that may be used with the same array to estimate arrival angles only is described. This approach has the advantage that it requires far fewer computations. The performance of this approach is compared with that of the original approach and with that of estimators using conventional ESPRIT arrays     

Improved polarization measurements using a modified three-antennatechnique

An improved three-antenna measurement of polarization that greatly reduces the uncertainty due to phase measurement errors is described. This technique is used to calibrate polarization standards and probes used in near-field antenna measurements     

An N*N optical multiplexer using a planar arrangement of two star couplers

The author describes the design of an integrated N*N multiplexer capable of simultaneously multiplexing and demultiplexing a large number (up to about 50) of input and output wavelength channels. The multiplexer is a generalization of the 2*2 Mach-Zehnder multiplexer. It consists of two N*M star couplers connected by M paths of unequal length. Aberrations caused by mutual coupling in the waveguide arrays are minimized by a correction scheme that causes each star coupler to accurately perform a Fourier transformation. The multiplexer should be useful as a wavelength routing device for long haul and local area networks.<>     

Crosstalk reduction in arrayed-waveguide grating multiplexer/demultiplexer using cascade connection

This paper proposes a cascade-connected arrayed-waveguide grating (AWG) as a solution to the problem of crosstalk accumulation in a large-scale AWG multiplexer/demultiplexer (MUX/DEMUX) and demonstrates a 64-channel cascaded AWG module with a very low background crosstalk of less than -80 dB and a total crosstalk of about -34 dB. In this paper, the authors densely integrate 64 additional compactly designed crosstalk-suppressing AWGs whose bandwidths were carefully optimized and directly attach them to a conventional 64-channel AWG. Consequently, in addition to a very low crosstalk, a low insertion loss and a compact size without passband shape distortion are achieved with this module. Based on the performance of the cascaded AWG module, it is then estimated that it is possible to realize a 1000-channel AWG MUX/DEMUX that is free from the problem of crosstalk accumulation.     

Measurement of depolarization ratio and ultimate limit ofpolarization crosstalk in silica-based waveguides by using a POLCR

A polarization optical low coherence reflectometer (POLCR) is described that enables us to excite only the transverse electric (TE) mode of a test waveguide and to measure its Rayleigh backscatter signal distributions in the TE and transverse magnetic (TM) modes at a spatial resolution of 0.3 mm. The depolarization ratios of silica-based waveguides with relative refractive index differences of Δ=0.45 and 0.75% are obtained as 0.14 and 0.10, respectively, by measuring the bias in the ratio between the distributions in the TM and TE modes of each waveguide. By using the depolarization ratios and the Rayleigh backscatter signal levels, we calculate the ultimate polarization crosstalks to be -53 and -51 dB over 1 km, respectively. The actual polarization crosstalks of previously fabricated waveguides are about 50 dB higher than their ultimate limits for the same length of fiber     

Fiber laser polarization tuning using a Bragg grating in a Hi-Bifiber

Single- and dual-wavelength tunable lasing (around 1552 nm) has been obtained in an Er-doped low-Bi fiber laser with a Bragg grating mirror in a Hi-Bi fiber. Equal output powers for both laser lines and spectral spacing of up to 0.26 mm, larger than the original spacing between the resonance peaks of the grating (0.2 nm), can be easily achieved by employing a polarization controller inside of the laser cavity     

一种高速阵列型多路复接器设计

在光电传感器的传输接口电路中,为了实现高速实时传输,需要将大量的低速并行数据转换成一路高速串行数据。文中采用Charted 0.35μm CMOS工艺,设计了一款8×8×14bit转1路的复接器。通过分析三种复接结构的特点,确定了使用混合型并串转换电路来降低功耗和设计复杂度。低速单元采用并行结构和串行结构来降低时钟树的设计难度;高速部分采用树型结构来实现半速设计,降低功耗。具体电路包括锁存器、选择器、门控开关、分频器以及时钟缓冲器等等。芯片工作在3.3V电源电压下,最高工作速率可达1.25Gbps。     

On the address inputs of a multiplexer

The digital multiplexer is useful in implementing switching functions. The implementation of some switching functions, however, requires an extra inverter. Sometimes, the need for an inverter can be obviated by suitably selecting the address inputs of the multiplexer. In an earlier paper, we presented a systematic method for selecting the address inputs of the multiplexer. This paper presents another simple systematic method for the same purpose. Unlike the previous method which makes use of a table, the method presented here makes use of a simple theorem.     

采用偏振分光棱镜的光桥式补偿技术

介绍了一种使用偏振分光棱的新型光桥式补偿技术，并对因棱镜消光比变化导致的误差进行了研究。基于该补偿结构的光纤压力传感器已实现应用于石化部门油罐储量计量，其现场运行的长期稳定性优于０．２％。     

Pulsewidth compression in optical components with polarization modedispersion using polarization controls

An algorithm capable of finding the input and output states of polarization for pulsewidth narrowing at the output of an optical fiber with polarization mode dispersion (PMD) is analytically presented and numerically solved. It has been demonstrated theoretically and experimentally that the output pulses can he narrower than the input pulses when PMD is compensated by controlling both the input polarization and the receiver polarization states. The cost of this improvement is a reduction of the optical power in the output pulse