光学小波变换中尺度因子的极限

分析了光学小波变换中实际光学系统对尺度因子选取的限制 ,确定了小波函数对应光学系统尺度因子的最小值 ,分别给出几种小波函数在 4 F系统中尺度因子的最小值 ,为小波变换应用于实际光信息处理系统提供了有意义的参考数据。     

Signal processing for optical communication

Optical communication plays a significant and increasing role in our society. The public demand for higher network speed requires an optical backbone network with larger capacity. Accompanying high transmission-rate optical communications system are severe technical specifications for optical devices and systems. Many popular optical devices could be represented with a digital filter model as described in this article. Use of well-developed signal processing techniques and algorithms to design these optical devices is a wise use of existing technology. The wavelength division multiplexing (WDM) system, which is the dominating optical communication system, is introduced in this article. Three signal processing application examples for optical communications are presented: optical wavelength interleaver, an all-pass filter for chromatic dispersion compensation, and an electronic equalizer. As demonstrated in this article, signal processing could play an important role in the development of advanced optical communication systems. However, as demonstrated in the case of an electronic equalizer, some optical system characteristics may require special attention if signal processing techniques are to be applied successfully. Therefore, interdisciplinary cooperation between researchers in optics and signal processing will be crucial for optical communications to fully benefit from signal processing.     

红外光学系统无热化设计研究

分析了温度对红外光学系统的影响。军用红外光学系统往往工作在温度变化较大的环境中,因此必须采取有效的温度补偿措施以减少离焦。介绍了红外光学系统无热化设计的方法及原理。根据小型红外光学系统的设计参数,提出了光学被动式无热化设计思路。试验结果表明,光学系统在0～60℃范围内可保持良好的成像效果。     

Optoelectronic Package Having Low-Loss Optical Waveguide Hole With Core–Clad Structure for Chip-to-Chip Interconnection

We have developed optoelectronic packages having optical waveguide holes with core–clad structures for chip-to-chip optical interconnection within computer systems. A rate of 10-Gb/s/ch chip-to-chip optical signal transmission has been demonstrated. The optoelectronic package we have developed consists of two guide pins and four-channel optical waveguide holes. The two guide pins are used to align an optical fiber connector with an optical device. The optical waveguide holes are used to transmit optical signals vertically through the optoelectronic package. Using the optical waveguide holes in the optoelectronic package, and high-quality signal transmission has been achieved.      

Spatial optical beam-forming network for receiving-mode multibeamarray antenna - proposal and experiment

This paper proposes an array antenna for multibeam reception with a beam-forming network (BFN) that uses spatial optical signal processing and also presents experimental results. In this antenna, signals received at individual antenna elements are converted to optical signals, and are optically divided from the directions of signal arrival by means of optical spatial Fourier transformation, and then the optical signals are reconverted into microwave signals at the BFN. In this BFN, to maintain optical path-length conditions, an optical integrated circuit is employed. We have experimentally investigated the optical signal processing performances of the BFN for multibeam reception. The experimental results show that optical beam direction is changed according to the signal arrival direction of an array antenna. Two multiple RF signals with different phase distributions are separated. The sidelobe level of the optical signal is reduced when amplitude distributions of optical signals are Chebyshev distributions. We also present the signal transmission behavior of this BFN. The measured carrier-to-noise-ratio degradation of this BFN is 2 dB at BER=10^-6 when 118.125-Mb/s QPSK modulated signal is input into the BFN     

Electromagnetic field photonic sensors

In this paper, we review the different configurations proposed for electromagnetic field optical sensing. Intrinsic and extrinsic optical fiber sensors for electric and magnetic field measurement are examined, including those realized jacketing the fiber by magnetostrictive, conductive, electrochromic and polymeric materials and those measuring induced strain by magnetostrictive, electrostrictive and piezoelectric transducers. Extrinsic optical fiber sensors exploiting magneto-optic, electro-optic and Joule effects are also presented.Moreover, integrated optical electric and magnetic field sensors in which microwave signal provided by an antenna modulates the optical signal generated by an optical source are reviewed. Finally, active and coupled resonators based on electric field sensors are investigated.     

一种基于相位调制器的40 GHz OFDM-ROF系统实验研究

实验研究了一种基于相位调制器(PM)并级联强度调制器(IM)实现40 GHz毫米波传输正交频分复用(OFDM)信号的光纤无线通信(ROF)系统。在中心站,采用20 GHz的射频(RF)信号驱动PM,调节驱动信号的强度,使输出的信号经光纤布拉格光栅(FBG)滤除中心载波后再送入IM。2.5 Gbit/s的OFDM信号直接调制在光毫米波上,经过50 km标准的单模光纤(SSMF)传输到基站。在基站,光调制信号经光电转换器(PD)转换成电调制信号,再与RF信号混频,恢复出基带OFDM信号。实验结果表明,在无色散补偿、误码率(BER)为10-3的条件下,下行链路中2.5 Gbit/s的OFDM信号经光纤传输50 km后,其功率代价小于1 dB,而且信号的星座图依然较好。     

On-Chip Optical Interconnect

We describe a cost-effective and low-power-consumption approach for on-chip optical interconnection. This approach includes an investigation into architectures, devices, and materials. We have proposed and fabricated a bonded structure of an Si-based optical layer on a large-scale integration (LSI) chip. The fabricated optical layer contains Si nanophotodiodes for optical detectors, which are coupled with SiON waveguides using surface-plasmon antennas. Optical signals were introduced to the optical layer and distributed to the Si nanophotodiodes. The output signals from the photodiodes were sent electrically to the transimpedance-amplifier circuitries in the LSI. The signals from the photodiodes triggered of the circuitries at 5 GHz. Since electrooptical modulators consume the most power in on-chip optical interconnect systems and require a large footprint, they are critical to establish on-chip optical interconnection. Two approaches are investigated: 1) an architecture using a fewer number of modulators and 2) high electrooptical coefficient materials.     

Mechanically Flexible Chip-to-Substrate Optical Interconnections Using Optical Pillars

We experimentally characterize the benefits of using surface-normal mechanically flexible optical waveguides, or optical pillars, for chip-to-substrate optical interconnection. In order to benchmark the performance of the optical pillars, the optical coupling efficiency from a light source to an optical aperture with and without an optical pillar is measured. For a light source with 12deg beam divergence, a 50times150 mum optical pillar improves the coupling efficiency by 2-4 dB compared to pillar-free (free-space) optical coupling. A 30times150 m optical pillar improves the coupling efficiency by 3-4.5 dB. This demonstrates the importance of using optical pillars when small photodetectors (PDs) and dense optical input/outputs (I/Os) are needed. The optical excess losses of 50times150 mum optical pillars are measured to be less than 0.2 dB. Due to the high mechanical flexibility of the pillars, we also demonstrate that optical pillars enhance the optical coupling efficiency between the chip and substrate when they are misaligned in the lateral direction. This is especially important since the coefficient of thermal expansion of the chip and substrate are often mismatched, and preserving optical alignment and interconnection between them is critical during thermal excursions. The lateral mechanical compliance of the optical pillars is also measured and can be as great as 30 mum/mN. The optical pillars are also shown to be compliant under a compressive force thus allowing the optical I/Os to be assembled on nonplanar surfaces such as low-cost organic substrates.     

Integrated optical devices of InGaAsP/InP heterojunction phototransistor and inner stripe light-emitting diode

New integrated optical devices combining an InGaAsP/InP HPT and an inner-stripe LED are proposed and their fabrication processes are described. The device functions of light amplification, optical bistability, and optical switching are demonstrated in the 1-µm wavelength region.     

Integrated optical/optoelectronic switch for parallel opticalinterconnects

A monolithic optical/optoelectronic switch for a reconfigurable, parallel optical interconnect is described. By integrating a vertical-cavity surface-emitting laser with a three-terminal GaAs-AlGaAs heterojunction phototransistor, the functions of an optical transceiver and an optical space switch are combined. Switching experiments demonstrate optical/optoelectronic switching and data conversion at 200 Mbit/s     

Multifrequency lasers and applications in WDM networks

The current status and applications of multifrequency lasers (MFL) are reviewed. An MFL consists of an array of N optical amplifiers monolithically integrated with a 1×N optical multiplexer. The laser provides the functionality of N independent lasers whose optical wavelengths are precisely locked together by the common intracavity optical multiplexer. The design of an MFL together with its fundamental characteristics are discussed, and state-of-the-art results are shown. The functionality of an MFL is compared to that of an integrated DFB array. Finally, we show some applications of single-wavelength tunable transmitters and multiwavelength transmitters     

全光时延线的实现和应用

从光时延线的原理、结构和性能等方面对全光时延线的实现方法进行了详述,并认为基于波长转换和光纤色散的全光可调时延线将在全光网络中具有重要作用;之后,对光时延线在OTDM、光学测量和光交换中的应用进行了介绍,最后总结了全光时延线需要改进的几个方面。     

Power reduction techniques for multiple-subcarrier modulated diffuse wireless optical channels

In this paper, two novel techniques are proposed to reduce the average optical power in wireless optical multiple- subcarrier modulated (MSM) systems, namely in-band trellis coding and out-of-band carrier design. Data transmission is confined to a bandwidth located near DC. By expanding the signal set and coding over the increased degrees of freedom, an in-band trellis coding technique achieved an average optical power reduction up to 0.95 dBo over conventional MSM systems while leaving the peak optical power nearly unaffected. With a symbol-by-symbol bias, the received DC level can be detected to provide a degree of diversity at the receiver. In this manner, an additional average optical power reduction up to 0.50 dBo together with a peak power reduction of 0.46 dBo is achieved. Moreover, the unregulated bandwidth available in wireless optical channels is exploited and out-of-band carrier signals are designed outside the data bandwidth to reduce the average optical power. Average optical power reduction as high as 2.56 dBo is realized at the expense of 4 out-of-band carriers and an increase in the peak optical power. Finally, combining the three techniques achieves the best average optical power reduction of 2.63 dB optical.     

Proposals and analyses on laser amplifier based integrated optical circuits

Simplified traveling wave laser (TWL) amplifier equations are given based on a lumped model. Pulse transfer characteristics for a TWL amplifier are examined theoretically. A new class of integrated optical amplifier with three terminals (OPATT) has been proposed as an optical analog of the electric transistor. Analytical formulas and dynamic properties of an OPATT have been considered. OPATT-based optical integrated circuits, including optical differential amplifiers, comparators, saturable oscillators, and optical logic gates, have been investigated theoretically.     

基于倍增FSR式光梳状滤波器阵列的瞬时频率测量研究

基于自由频谱区(FSR)倍数增长式光梳状滤波器阵列,设计了一种微波瞬时频率测量方案,实现了具有自然二进制编码的数字输出。待测微波信号经过载波抑制型单边带调制后加载到光波上产生一阶边带,而后将其输入到光梳状滤波器阵列中;阵列由多个梳状滤波器并联而成,它们滤波响应对应的FSR呈倍数增长趋势,最高位数字输出对应滤波器的FSR最大。滤波后输出的光信号经光电检测、比较和判决后,获得N位自然二进制码标识的频率值,提高了编码效率和测量精度。最后,在0～40GHz范围,验证了4位有效长度的数字编码式测频结果。     

Optical packet switching and buffering by using all-optical signal processing methods

We present a 1 /spl times/ 2 all-optical packet switch. All the processing of the header information is carried out in the optical domain. The optical headers are recognized by employing the two-pulse correlation principle in a semiconductor laser amplifier in loop optical mirror (SLALOM) configuration. The processed header information is stored in an optical flip-flop memory that is based on a symmetric configuration of two coupled lasers. The optical flip-flop memory drives a wavelength routing switch that is based on cross-gain modulation in a semiconductor optical amplifier. We also present an alternative optical packet routing concept that can be used for all-optical buffering of data packets. In this case, an optical threshold function that is based on a asymmetric configuration of two coupled lasers is used to drive a wavelength routing switch. Experimental results are presented for both the 1 /spl times/ 2 optical packet switch and the optical buffer switch.     

Wavelength selective optical logic and interconnects

A wavelength selective optical logic (WSOL) element that uses monolithically integrated wavelength selective optical input and output elements is described. Input optical signals are detected by photothyristors situated in an optical cavity which provides a highly selective response of a wavelength determined by the fabrication process. Output signals are generated by vertical cavity surface emitting lasers, whose lasing wavelengths can also be specified during the fabrication process. A vertical integration of these input and output elements that is suitable for wavelength selective optical logic and wavelength selective optical interconnect applications is proposed. The proposed circuitry is easily cascadable so that arbitrarily complex optical logic functions can be performed by WSOL devices in series. Several of the possible logic functions are described, including OR and AND gates, an adder, and a flip-flop     

光学空间通信进展

回顾了光学空间通信的发展，介绍了美国、日本及欧空局光学空间通信的研究现状和光学空间通信系统，并对我国光学空间通信系统的发展提出了建议。