A novel optical modulator system with enhanced linearizationproperties

The authors propose a novel optical modulator system that has the properties of having a null third-order intermodulation distortion (IMD); a spurious signal free dynamic range in excess of 100 dB as determined by the second-, fourth-, and fifth-order IMD; and a linear dynamic range of 2.46 radians. It is shown that a combination of a tandem of two directional couplers has the property of eliminating completely third-order IMD term, gives a large spurious signal free dynamic range, and provides a simple and practical solution to the problem of linearization of optical modulators     

相位调制器实现光标记交换的新方案

提出了一种利用相位调制器实现一阶边带抑制的光标记交换(OLS)技术的新方案,在中心载波和其余生成的多个副边带分别进行强度调制,实验产生10Gb/s非归零(NRZ)光载荷和2.5Gb/s垂直频分复用(OFDM)光标记信号,并分别在单模光纤中传输了50km。分析了基本原理,进而建立了一简单的系统理论模型,最后通过仿真和实验相结合的方法验证了方案的可行性。     

A novel optical bistable multiple-quantum-well phase modulator

The authors present a new type of optically bistable phase modulator utilizing a self electrooptic effect device (SEED) integrated with an electrooptic wavelength modulator. An electrically bistable SEED, operating on the principle of the quantum-confined Stark effect, controls the bias voltage across an electrooptic waveguide phase modulator to produce optical bistability. A control signal at 0.848 μm, corresponding to the first electron to heavy hole exciton transition in GaAs/AlGaAs multiple-quantum-well is used to switch 1.152 μm light propagating through a waveguide in a direction normal to the control beam     

DWDM optical millimeter-wave generation for radio-over-fiber using an optical phase modulator and an optical interleaver

We have proposed and experimentally demonstrated a novel scheme to generate a dense wavelength-division multiplexing (DWDM) optical millimeter-wave source by using an optical phase modulator and an optical interleaver. The stability of the DWDM optical millimeter wave generation is largely improved because we use an optical phase modulator without a dc-bias controller and an optical interleaver is subsequently employed to suppress the optical carrier of the DWDM source, which is not as temperature sensitive as a fiber Bragg grating. Moreover, the limitation of chromatic dispersion is greatly reduced due to avoiding the generation of higher order sidebands via driving the phase modulator with optimized RF signal.     

Low detection penalty in an optical DPSK heterodyne system using asaturated optical amplifier as phase modulator

A model established from the rate equations of a near traveling-wave optical amplifier (NTWOA) used as a phase modulator shows that the modulation rate is limited by the carrier lifetime to 500 Mb/s and that the worst-case detection penalty is about 0.7 dB. It is then experimentally demonstrated that close control of the injected light polarization can reduce the detection penalty in a DPSK (differential phase-shift keying) heterodyne system, using an NTWOA phase modulator instead of an LiNbO₃ modulator, to 0.6 dB. This device and a balance receiver have allowed the implementation of 282-Mb/s DPSK link operating at 1.522 μm over 242 km of fiber with a 3-dB margin     

Electrically tunable delay line using an optical single-side-band modulator

The authors propose a tunable delay line using an optical single-side-band modulator, a fiber Bragg grating and an optical fiber loop. The number of times light circulates in the loop can be controlled by the electric signal fed to the modulator. Packets of any lengths can go through the proposed delay line without any collisions, even if the length of the packet is larger than that of the delay loop.     

基于相位调制器倍频技术产生56 GHz毫米波的光载无线通信系统

提出并实验研究了一种基于光相位调制器(PM)倍频技术产生56GHz毫米波的光载无线通信(RoF)系统。在中心站,通过28GHz射频(RF)信号驱动PM产生了56GHz光毫米波,并将下行的2.8Gb/s开关键控(OOK)信号调制到该光载波上,然后经过20km标准单模光纤(SSMF)传输至基站,最后由天线进行发射。用户终端接收后,采用相干解调恢复出基带信号。实验结果表明,56GHz光载毫米波信号经SSMF传输20km后其功率代价小于1dB,通过无线方式传输1.1m后其功率代价小于2.5dB。     

Dispersion penalty reduction using an optical modulator with adjustable chirp

Using a unique Ti:LiNbO/sub 3/ modulator, the value of the modulation chirp parameter that minimizes the transmission power penalty caused by fiber chromatic dispersion was experimentally identified. System experiments at 5 Gb/s using nonreturn-to-zero (NRZ) amplitude-shift-keyed (ASK) transmission with direct detection reception are discussed, and the optimum values of the modulation chirp parameter versus distance for transmission at 1.5 mu m wavelength over fibre having zero dispersion at 1.3 mu m are identified. 5 Gb/s NRZ transmission was achieved through distances of 128, 192, and 256 km of conventional fiber while incurring dispersion penalties of -0.5, 0.1, and 1.1 dB respectively, by operating at the quantum chirp value.<>     

Stable photonic millimeter-wave generation using an integrated reciprocating optical modulator

We investigated stability and phase noise of V-band millimeter-wave generated by using a hybrid integrated reciprocating optical modulator consisting of a pair of fiber Bragg gratings and a LiNbO/sub 3/ optical phase modulator. The amplitude fluctuation of generated millimeter-wave was less than 1% without using feedback stabilization technique. Phase noise of the millimeter-wave was -74.3 dBc/Hz at 10-kHz offset.     

A novel optical phase modulator design suitable for phased arrays

A new design of optical phase modulator in SIMOX has been demonstrated, which allows duplication of active waveguides with a minimum requirement for external contacts and metallization. The device is based on a common cathode configuration and requires 56.5 mA at 1.65 V to produce a π-phase shift. To confirm the experimental results, the same device structure has been modeled, and provided good agreement, with V_π calculated to 1.70 V and 52.6 mA     

High speed sample and hold design using closed-loop pole-zero cancelation

A new closed loop Sample-and-Hold (S&H) architecture is proposed for pipeline analog-to-digital converter (ADC) that breaks the precision-speed-power trade off by means of canceling out the first closed loop pole. This pole-canceling results in widening the bandwidth of the S&H up to the second pole. In this architecture, two amplifiers are used: one for accuracy with little power consumption, another one for high-speed response, which consumes most of the total power. Exploiting these two amplifiers remedies some of the tradeoffs and limitations of opamp design in S&H circuits. Simulated by HSPICE with a standard BSIM3v3 0.13 μm technology, the S&H achieves 80 dB SFDR for a 1.6 V_ppd output at 500 MHz sampling rate.     

A precision autozeroing sample and hold integrated circuit

A precision sample and hold integrated circuit with autozeroing of all DC errors is described. Experimental data have shown that it provides the accuracy necessary for use in 12 bit data acquisition systems. Application of noise-optimized silicon gate FET devices for the input circuitry of amplifiers which buffer the hold capacitor results in a low droop rate and allows the sample/hold to operate without external components. Common mode rejection is optimized through implementation of a modified current source offering extremely high output impedance at high operating currents. The device includes all digital control and switching circuitry.     

A bridge type optoelectronic sample and hold circuit

A novel bridge-type optoelectronic (OE) sample-and-hold circuit based on current steering is proposed and experimentally tested. Experimental comparison between this circuit and the conventional direct OE sample-and-hold circuit shows that the bridge type is clearly superior in performance to the direct OE circuit. When a high speed signal is sampled with high accuracy, the bridge-type OE sample-and-hold is potentially more advantageous over the conventional electronic sample and hold in terms of large charging current capability, commanding signal isolation, fabrication simplicity, accurate timing control, and less time jitter     

10Gb/s TSC-HBT光调制器驱动电路设计

将TSC－HBT应用于HBT光调制器驱动电路的设计中。SPICE模拟结果显示，眼图张开形状良好，可以满足10Gbit/s光发射模块应用的要求。     

A complete monolithic sample/hold amplifier

A monolithic sample/hold amplifier is described which includes the holding capacitor on the chip. System design considerations and tradeoffs are discussed, as well as the circuit design details. High performance is achieved by the use of a process which produces bipolar transistors and p-channel silicon-gate FET's (SIGFET's) on the same chip. Performance characteristics obtained include an acquisition time of 10 /spl mu/s (20-V step), an aperture delay time of 80 ns, and a droop rate of 30 mV/s.     

利用相位和强度调制器产生高消光比超短光脉冲

提出了一种产生高消光比超短光脉冲的新方法.利用相位调制器调制连续光生成啾啁光,而后利用M-Z强度调制器的倍频调制抑制对压缩不利的啁啾部分的影响,再通过等效啁啾光纤光栅进行压缩产生光脉冲.理论和仿真结果表明,该方法可以很好地消除光脉冲的基底及减小旁辦,产生消光比大于30 dB、波形理想的光脉冲,具有很强的可实现性.最后利用实际制作的色散系数为-380 ps/nm的等效啁啾光纤光栅对该方法进行了实验验证,结果表明,在重复频率为2.5 GHz、相位调制系数为9时,可产生脉宽小于18 ps的高质量光脉冲.     

An improved approach of optical loss measurement using photocurrent and optical transmission in an electroabsorption modulator

We report an improved method to extract the optical absorption coefficient of a semiconductor electroabsorption modulator. Only the transmission and photocurrent data are needed with this method. The method makes it possible to obtain the optical coupling efficiency between laser and modulator, photocurrent conversion efficiency, and optical absorption coefficients from experimental data.     

Ultrafast differential sample and hold using low-temperature-grownGaAs MSM for photonic A/D conversion

This letter demonstrates an ultrafast sample and hold circuit using optically triggered metal-semiconductor-metal switches made of low-temperature-grown GaAs for use in a photonic analog-to-digital conversion system. A differential configuration is incorporated to reduce feedthrough noise     

Multiplexing optical sensors using spatial light modulator

Most optical sensor multiplexing systems results in a decrease in signal to noise ratio for each additional sensor added to the network. A technique using a spatial light modulator (SLM) which overcomes this problem is described. The techniques has been tested in a system which addresses eight photoelastic strain sensors.<>