Modeling O/E characteristics of 40-gb/s InGaAs side-illuminated waveguide photodiode submodule for optical receivers

In this paper, the circuit models of a waveguide photodiode (WGPD) and its submodule were investigated, and the O/E characteristics of a WGPD submodule are examined. Test structures of the WGPD and WGPD submodule were fabricated and microwave return loss (S11) was measured and compared with simulated data to validate the circuit models. With the established submodule model, optical to electrical (O/E) characteristics were measured and compared with the modeled data to analyze the effects of model parameters on the submodule performance. Based on the results, it can be concluded that the suggested submodule model can explain the characteristics of the submodule performance. In addition, parasitic components that originated from the ribbon bonding block can crucially impact on the performance of WGPD submodule.     

Serial dark soliton for 100-gb/s applications

We analyze the performance through numerical simulations of a new modulation format: serial dark soliton (SDS) for wide-area 100-Gb/s applications. We compare the performance of the SDS with conventional dark soliton, amplitude-modulation phase-shift keying (also known as duobinary), nonreturn-to-zero, and return-to-zero modulation formats, when subjected to typical wide-area-network impairments. We show that the SDS has a strong chromatic dispersion and polarization-mode-dispersion tolerance, while maintaining a compact spectrum suitable for strong filtering requirement in ultradense wavelength-division-multiplexing applications. The SDS can be generated using commercially available components for 40-Gb/s applications and is cost efficient when compared with other 100-Gb/s electrical-time-division-multiplexing systems.     

Monolithic demodulator for 40-gb/s DQPSK using a star coupler

A novel device that demodulates both quadratures of the optical differential quadrature phase-shift keying (DQPSK) format in a single interferometer by using a 4 /spl times/ 4 star coupler was demonstrated. Simultaneous measurements of both DQPSK quadratures at 42.7 Gb/s are also presented.     

10-gb/s operation of an In/sub 0.53/Ga/sub 0.47/As p-i-n photodiode on metamorphic InGaP buffered semi-insulating GaAs substrate

The SONET OC-192 receiving performance of In/sub 0.53/Ga/sub 0.47/As p-i-n photodiode grown on linearly graded metamorphic In/sub x/Ga/sub 1-x/P buffered GaAs substrate is reported. With a low-cost TO-46 package, such a device exhibits a frequency bandwidth up to 8 GHz, a bit-error rate (BER) of 10/sup -9/ at 10 Gb/s, a sensitivity of -17.8 dBm, and a noise equivalent power of 3.4/spl times/10/sup -15/ W/Hz/sup 1/2/ owing to its ultralow dark current of 3.6/spl times/10/sup -7/ A/cm/sup 2/. Eye diagram analysis at 10 Gb/s without transimpedance amplification reveals a statistically distributed Q-factor of 8.21, corresponding to a minimum BER of 1.1/spl times/10/sup -16/ at receiving power of -6 dBm.     

A 1.25-gb/s burst-mode receiver for GPON applications

This paper presents a 1.25-Gb/s burst-mode receiver (BMRx) for upstream transmission over gigabit passive optical networks (G-PONs). The dc-coupled receiver uses a unique arrangement of three limiting amplifiers to convert the bursty input signal to a current mode logic output signal while rejecting the dc offset from a preceding transimpedance amplifier. Peak detectors extract a decision threshold from a sequence of 12 successive nonreturn-to-zero (NRZ) 1's and 12 successive NRZ 0's received at the beginning of each packet. Automatic compensation of the remaining offsets of the BMRx is performed digitally via digital-to-analog converters. The chip was designed in a 0.35-/spl mu/m SiGe BiCMOS process. The receiver contains an APD with a gain of 6 and a transimpedance amplifier and shows a sensitivity of -32.8 dBm and a dynamic range of 23.8 dB. A sensitivity penalty of 2.2 dB is incurred when a packet with average optical power of -9 dBm precedes the packet under consideration, the guard time between the packets being 25.6 ns. The BMRx includes activity detection circuitry, capable of quickly detecting average optical levels as low as -35.5 dBm. The performed measurements prove that the receiver meets the G-PON physical media dependent layer specification defined in ITU-T Recommendation G.984.2.     

Design, optimization, and fabrication of side-illuminated p-i-nphotodetectors with high responsivity and high alignment tolerance for1.3and 1.55-μm wavelength use

We describe the design, optimization and fabrication of side-illuminated p-i-n photodetectors, grown on InP substrate, suitable for surface hybrid integration in low-cost modules. The targeted functionalities of these photodetectors were a very high responsivity at 1.3- and 1.55-μm wavelengths and quasi-independent on the optical polarization, and had a high alignment tolerance. Moreover, in order to avoid any reliability problem, the principle of evanescent coupling was adopted. Two photodetectors were optimized, fabricated, and tested; the first was for classical cleaved fiber, and the second was for lensed fiber. Because the considered epitaxial structures were complicated to optimize, the method of the genetic algorithm was used, associated with a beam propagation method (BPM). The photodetectors are based on multimode diluted waveguides, which are promising structures in the field of optoelectronics and integrated optics. Starting from the presented comparisons between experimental and theoretical results, the interest of the design method is discussed and the complete performances of newly fabricated devices are presented. The aspect of the cutoff frequency is also considered     

Payload-envelope detection and label-detection integrated photonic circuit for asynchronous variable-length optical-packet switching with 40-gb/s RZ payloads and 10-gb/s NRZ labels

A photonic integrated circuit that performs 40-Gb/s payload-envelope detection (PED) and 10-Gb/s label detection for asynchronous variable-length optical-packet switching is demonstrated. The circuit consists of an InP photonic integrated device combined with electronic GaAs and InP devices on a carrier. Asynchronous variable-length optical packets with 40-Gb/s return-to-zero (RZ) payloads and 10-Gb/s non-RZ (NRZ) labels are processed by the circuit. The circuit outputs a PED electrical signal that represents the temporal location of the payload and a 10-Gb/s electrical signal representing the optical label. The optical label is detected error free. The PED signal has a rise/fall time of 3-ns and 150-ps jitter. The PED signal was also used to erase and rewrite the optical labels error free.     

40-gb/s EA modulators with wide temperature operation and negative chirp

Broad bandwidth external modulators are widely used in optical fiber networks to avoid the chirp associated with the direct modulation of laser diode sources. For transmission application beyond 10 Gb/s, electroabsorption modulators (EAMs) offer many advantages such as low drive voltage, low chirp characteristics, small size, and added functionality through integration with a distributed feedback laser. In this letter, we present static and dynamic characterization of an EAM demonstrating the possibility to have with the same device uncooled operation at 40 Gb/s and negative chirp at low negative bias. These features are attractive for cost reduction in short link applications and for long-haul transmission. All the measurements are performed at 40 Gb/s from room temperature up to 60/spl deg/C demonstrating a negative chirp behavior for the stand-alone modulator over the entire temperature range.     

Cryogenic performance of a high-speed GaInAs/InP p-i-n photodiode

The cryogenic performance of a high-speed GaInAs/InP p-i-n photodiode, with graded bandgap layers at the heterostructure interfaces, was investigated for the first time. DC measurements show that the dark current of the diode decreases sharply as the temperature decreases from 300 to 200 K. A factor of 1000 in dark current reduction was found for this photodiode, when it was cooled from room temperature to about 150 K. Similar modulation bandwidths were found for this device for temperatures between 9 and 300 K, with a bandwidth greater than 20 GHz. No degradation was found in performance at cryogenic temperature compared to room temperature. This enables direct integration of high-speed photodiodes with superconductive and other cryogenic electronics     

CMOS photodiode with enhanced responsivity for the UV/blue spectralrange

A new photodiode for the UV/blue spectral range, which can be integrated monolithically with CMOS circuits, is presented. Such optoelectronic integrated circuits (OEICs) with a high sensitivity in the UV/blue spectral range are needed in near-future optical storage systems like digital versatile disk (DVD) or digital video recording (DVR). At 400 nm, our so-called finger photodiode achieves a responsivity of 0.23 A/W corresponding to a quantum efficiency η of 70% [with an antireflection coating (ARC)] and rise and fall times of 1.0 ns and 1.1 ns, respectively. The finger photodiode can be used in the red spectral range, too. At 638 nm, the responsivity is 0.49 A/W (η=95%) and rise and fall times of less than 2.3 ns are achieved. For the integration of the finger photodiode in an industrial 1 μm twin-well CMOS process, only one additional mask is needed in order to block out the threshold voltage implantation in the photo-active region     

A 40-gb/s InGaAlAs-InAlAs MQW n-i-n Mach-Zehnder Modulator with a drive Voltage of 2.3 V

We have developed a traveling-wave Mach-Zehnder modulator using an n-i-n heterostructure fabricated on an InP substrate. We obtained an extremely small /spl pi/ voltage (V/spl pi/) of 2.2 V, even for a short signal-electrode length of 3 mm. We confirmed that the device has an impedance-matched electrode and operates at 40 Gb/s with a single-ended drive voltage of 2.3 V.     

All-optical payload envelope detection for variable length 40-gb/s optically labeled packets

We demonstrate a new technique to all-optically identify the precise temporal locations and durations of the payloads of optical packets consisting of a variable length 40-Gb/s return-to-zero payload and 10-Gb/s nonreturn-to-zero label. The all-optically generated payload envelope signal can be used to erase the original optical label and rewrite a new label. The recovered payload envelope has 300-ps rise time and edge root-mean-square average jitter of 30 ps over a 10-dB dynamic range of input optical packet power. These numbers indicate that this technique enables the use of very short guard bands between payloads. The technique is demonstrated using optical semiconductor devices that are straightforward to monolithically integrate on a single chip.     

Optical 40-gb/s 3R regenerator with a combination of the SPM and XAM effects for all-optical networks

An all-optical 3R regenerator with a combination of self-phase modulation (SPM) and cross-absorption modulation (XAM) effects is proposed and investigated. Principle performances of the proposed all-optical 3R regenerator were experimentally investigated at a signal bit rate of 40 Gb/s. The all-optical 3R regenerator, which is located at the midpoint of a 1080-km transmission line, successfully provided an approximately 3-dB improvement of the Q-factor both just after regeneration and after totally 1080-km transmission. The chromatic dispersion tolerance of the proposed 3R regenerator was also investigated and successfully enhanced to about twice as wide by introducing a predistortion block configuration including a highly nonlinear fiber (HNLF). It was confirmed that the proposed all-optical 3R regenerator can become one of the strong candidates for the actual deployment of the all-optical network.     

320-to-40-gb/s demultiplexing using a single SOA assisted by an optical filter

We demonstrate excellent all-optical demultiplexing of 40-Gb/s base-rate channels out of 160- and 320-Gb/s single polarization optical time-division-multiplexed data streams. The demultiplexer utilizes a semiconductor optical amplifier and an optical filter placed at the amplifier output. The center wavelength of the filter is blue-shifted from the wavelength of the clock signal, so that ultrafast chirp dynamics can be employed for optical switching. Error-free demultiplexing was achieved at very low optical switch powers: 3.5 mW (160-Gb/s data), 6.3 mW (320-Gb/s data), and 0.09 mW (40-GHz clock). The proposed demultiplexer has a simple structure and allows monolithic integration.     

Analysis of high speed p-i-n photodiode S-parameters by a novel small-signal equivalent circuit model

A novel small-signal radio frequency (RF) equivalent-circuit of the side-illuminated input tapered waveguide-integrated p-i-n photodiodes (WG PIN PD) is proposed. The proposed RF equivalent-circuit involves both the carrier-transit effect and the external resistance-capacitance (RC) time constant limitation on the frequency response of the p-i-n PD. The carrier-transit effect is realized by adding an RC circuit to an ideal voltage-controlled current source as the input opto-RF equivalent circuit. The carrier transit-time effect is equivalently represented by the time-constant of this input RC circuit. This new equivalent circuit model fits well with both the measured reflection and optoelectronic conversion parameters of the WG PIN PD in a broad frequency range from 45 MHz to 50 GHz.     

高速近红外InGaAs/InP单光子探测器设计

量子信息技术的研究中大量采用单光子作为量子 信息的载体,因此单光子探测技术成为近来研究的 热点。目前基于InGaAs/InP雪崩光电二极管(APD)的单光子探测器(SPD)工作频率较低 且无法连续可 调。高速门控模式下,APD的容性效应会带来较强的尖峰噪声将光生雪崩信号湮没,导致探 测器的探测效 率也相对较低。为了提高单光子探测器的工作频率,降低后脉冲概率,设计了基于高速正弦 门控技术的 InGaAs/InP雪崩光电二极管淬灭-重置电路。为了抑制强大的背景噪声提高探测效率,设 计了双APD平衡 方案来提取有效雪崩信号。实验结果表明:设计的探测器工作频率连续可调;在－ 50℃、1～1.3GHz门控频率 条件下,最光子大探测效率为35%,暗计数率为4.2×10 －5/gate。探测效率为18%时 ,暗计数率仅为5.6×10－6/gate,后脉冲概率均低于5×10－6/ns。     

Eight-channel p-i-n/HBT monolithic receiver array at 2.5 Gb/s perchannel for WDM applications

We report a monolithic chip incorporating an eight channel p-i-n/HBT photoreceiver array designed for multichannel WDM applications. The p-i-n photodetectors are edge illuminated and centered at a 250 μm pitch for mating with either ribbon fiber connectors or waveguide demultiplexers. Each channel operates at 2.5 Gb/s with an electrical crosstalk of -20 dB between adjacent channels. The average sensitivity of each receiver in the array was measured to be (-20±1) dBm for a bit error rate of 10^-9 at a wavelength of 1.5 μm     

Improvement of dispersion tolerance using phase-Modulated NRZ signals in 40-gb/s transmission systems

Compared with the conventional nonreturn-to-zero (NRZ), return-to-zero (RZ), carrier-suppressed return-to-zero, and chirped RZ signals by numerical simulation, a higher dispersion tolerance in the presence of fiber nonlinearities and amplifier noise has been obtained in this letter by using the phase-modulated NRZ signals. This scheme aims to improve resistance to residual dispersion by an adapted phase modulation at the transmitter.     

A 5-b 10-GSample/s a/D converter for 10-gb/s optical receivers

A 5-b flash A/D converter (ADC) is developed in an 0.18-/spl mu/m SiGe BiCMOS that supports sampling rates of 10 Gsample/s. The ADC is optimized to operate in digital equalizers for 10-Gb/s optical receivers, where the ADC has to deliver over three effective number of bits (ENOBs) at Nyquist. A fully differential flash ADC incorporating a wide-band track-and-hold amplifier (THA), a differential resistive ladder, an interpolation technique, and a high-speed comparator design is derived to resolve the aperture jitter and metastability error. The ADC achieves better than 4.1 effective bits for lower input frequencies and three effective bits for Nyquist input at 10 GS/s. The ADC dissipates about 3.6 W at the maximum clock rate of 10 GS/s while operating from dual -3.7/-3V supplies and occupies 3/spl times/3mm/sup 2/ of chip area.     

Nonstationary and nonlinear response of a p-i-n photodiode made ofa two-valley semiconductor

The influence of nonstationary and nonlinear effects on carrier transport in a p-i-n photodiode made of a two-valley semiconductor is analyzed. A phenomenological model based on a two-valley conduction-band model is used, incorporating transition rates for intervalley electron transfer into the continuity equations and the drift-diffusion equations for carrier transport. A large optical power absorption in a small device can perturb, via the space-charge potential, the electric field which governs the carrier transport, and thus give rise to a nonlinear electrical response. The influence of these effects on photodiode response to pulsed light stimulation under various reverse-bias voltages is calculated