10-Gb/s Transmission on Single-Wavelength Multichannel SCM-Based FDDI-Grade MMF Links at Lengths Over 300 m: A Statistical Investigation

We propose and comprehensively investigate a subcarrier-multiplexing (SCM) system based on 62.5-mum-core-diameter multimode fiber (MMF) using a single wavelength to achieve 10-Gb/s transmission over link lengths beyond 300 m, using 1.3-mum-wavelength lasers with radial offset launch into MMF links. The system utilizes multichannel SCM transmission using quadrature-phase-shift-keyed modulation in combining baseband transmission with three passband SCM channels at the carrier frequencies of 3.75, 6.25, and 8.75 GHz while incorporating a maximum laser modulation bandwidth of 10 GHz to ensure system compliance with the limits of current uncooled laser devices. A statistical investigation of the system highlights its capability to achieve an acceptable yield over worst-case MMF links of length 600 m. We also investigate the improvement in system performance granted by allowing a controlled overlap of frequency spectra of the passband SCM channels. In addition, we test the accuracy of the previously proposed usable average slope criterion of less than 4 dB/GHz, which is needed to achieve low-penalty transmission with eye-closure penalties <3 dB.     

Loss characteristics of helical-core fiber

A special optical fiber is investigated,which has a helical core in the cylindrical cladding.The beam propagation method(BPM) is used for analyzing the impacts of the geometric and physical parameters on the properties of mode losses of the helical-core fiber.The propagation loss is 0.32 dB/m for the fundamental mode and the propagation loss is 20.95 dB/m for the LP11 mode in the wavelength range of 1050-1065 nm when the core diameter is 19 μm,the pitch of the core’s helix is 2.66 mm,and the offset of the helix core from the center of the fiber axis is 31 μm.The core diameter of the single-mode helical-core fiber well exceeds that of the conventional large-mode-area fiber.The helical-core fiber can provide the effective large-mode-area single-mode operation without coiling fiber or selecting excitation mode.     

Evolution of the beam diameter in a multimode fiber link throughoffset connectors

We find that using an overfilled launch, transmission of an 8-Gb/s nonreturn-to-zero (NRZ) signal can suffer a significant power penalty due to modal noise or fiber bandwidth fluctuations if an offset connector is located before the 300-m-long multimode fiber link. This is an important problem as multimode fiber links in the premises typically contain several (potentially offset) connectors. A possible solution in state-of-the-art multimode fibers having a small refractive index center defect is to employ a single-mode center launch. To evaluate the robustness of this technique in the presence of several offset connectors in the link, a thorough study of the evolution of the beam diameter is performed. It suggests that at least five standard connectors may be employed without incurring significant power penalties     

On the performance of the electrical equalization technique in MMF links for 10-gigabit ethernet

In this paper, the electrical equalization technique utilized in multimode fiber (MMF) links for 10-Gigabit Ethernet is reported. This paper presents and compares three kinds of equalizers: linear equalizer, decision feedback equalizer (DFE), and a nonlinear finite-impulse-response DFE (NL-FIR-DFE) based on the analysis of nonlinear operations of direct modulation and detection in MMF links. Computer simulations reveal that NL-FIR-DFE exhibits superior performance in comparison with normal DFE. The equalization performance for an MMF channel with bandwidth 500 MHz-km as well as 160 MHz-km is demonstrated. It is demonstrated that with direct modulation of cost-effective vertical-cavity surface-emitting laser (VCSEL) or Fabry-Perot laser, the transmission distance for installed MMF with a bandwidth of 500 MHz-km at 10 Gb/s can be extended to 300 m with an appropriate offset restricted mode launch condition by utilizing normal DFE and to more than 650 m for NL-FIR-DFE. Moreover, it is shown that the transmission distance for an MMF with a bandwidth of 160 MHz-km can reach 300 m with more than seven times bandwidth improvement by using NL-FIR-DFE.     

Tunable and coherent nanosecond 7.2–12.2 μm mid-infrared generation based on difference frequency mixing in ZnGeP2 crystal

A coherent mid-infrared laser source, which can be tuned from 7.2 μm to 12.2 μm based on the type-II phase-matched difference frequency generation (DFG) in an uncoated ZnGeP₂ (ZGP) crystal, is reported. The two pump waves are from a type-II phase-matched dual-wavelength KTP optical parametric oscillator (OPO) of which the signal and idler waves are tuned during 1.85–1.96 μm (extraordinary wave) and 2.5–2.33 μm (ordinary wave), respectively. The maximum energy of the generated mid-infrared laser is 10 μJ at 9.22 μm, corresponding to the peak power of 2.2 kW.     

A 0.18 μm CMOS TIA Plus Limiting Amplifier with a 5.3 GHz Overall Bandwidth for Fiber Optic Communications

A shunt series feedback transimpedance amplifier (TIA), based on a current amplifier using a zero–pole cancellation, followed by a 6 stages limiting amplifier (LA), proves to be suitable as receiver front-end for a 8 Gb/s communications over fiber optic. The front-end is realized with a 0.18 μm CMOS technology, and shows the following performances: the TIA has a 50 dBΩ transimpedance gain and 5.5 GHz bandwidth, the LA has a 46 dB gain and 7.9 GHz bandwidth. The differential voltage swing at the output is 300 mV. The total power consumption is 112 mW.     

Widely and continuously tunable optical parametric generator based on MgO-doped periodically poled LiNbO3 crystal

Pulsed optical parametric generators(OPGs)and op-tical parametric oscillators(OPOs)have beenextensive-ly studied and developedfor generatingtunable coherentsources[1-5]that cover the wide spectral range fromthenear UVto the mid IR.In this letter we report…     

Measurement of surface recombination velocity and bulk lifetime in Si wafers by the kinetics of excess thermal emission

A contactless nondestructive technique for measuring recombination parameters (surface recombination velocity and bulk and effective lifetime of free carriers) in Si wafers is proposed. The technique is based on the analysis of the relaxation kinetics of excess thermal emission of a wafer beyond the Si intrinsic absorption edge (λ > 3 μm) after excitation by a short laser pulse with a photon energy higher than the Si band gap. Experimental results for wafers 300 μm and 2 mm thick, excited by laser radiation with wavelengths of 0.96 and 1.06 μm at above-room temperatures are presented. The surface and bulk components of the effective lifetime are separated by extrapolating the final portion of the kinetics of excess thermal emission relaxation to the intersection with the y coordinate axis.     

445 Mbit/s transmission field experiment at 1.55-µm wavelength region over 80 km using undersea optical-fiber cable

New transmission equipment employing a 1.55-μm distributed feedback laser diode (DFB-LD) to overcome fiber dispersion has been tested at environmental conditions using 1.3-μm zero-dispersion fiber cable on the undersea section of route F-400M. The DFB-LD's dynamic spectrum characteristics, in relation to power penalty, were examined and a suitable laser prebias control level was obtained. Field experimental transmission lines operated error free for a two-month period, and applicability to 1.55-μm 445-Mbit/s systems of over 100 km was shown.     

Submicron nickel filaments made by electroplating carbon filaments as a new filler material for electromagnetic interference shielding

Short nickel filaments of diam 0.4 μm and containing 94 vol% Ni and 6 vol% C were fabricated by electroplating with nickel 0.1 μm diam catalytically grown carbon filaments. The use of these filaments in polyether sulfone in amounts of 3, 7,13, and 19 vol% gave composites with electromagnetic interference shielding effectiveness at 1–2 GHz of 42,87,84, and 92 dB, respectively, compared to a value of 90 dB for solid copper. Less shielding was attained when 0.1 μm diam carbon filaments or 2 or 20 μm diam nickel fibers were used instead.     

Integrated transversal equalizers in high-speed fiber-optic systems

Intersymbol interference (ISI) caused by intermodal dispersion in multimode fibers is the major limiting factor in the achievable data rate or transmission distance in high-speed multimode fiber-optic links for local area networks applications. Compared with optical-domain and other electrical-domain dispersion compensation methods, equalization with transversal filters based on distributed circuit techniques presents a cost-effective and low-power solution. The design of integrated distributed transversal equalizers is described in detail with focus on delay lines and gain stages. This seven-tap distributed transversal equalizer prototype has been implemented in a commercial 0.18-/spl mu/m SiGe BiCMOS process for 10-Gb/s multimode fiber-optic links. A seven-tap distributed transversal equalizer reduces the ISI of a 10-Gb/s signal after 800 m of 50-/spl mu/m multimode fiber from 5 to 1.38 dB, and improves the bit-error rate from about 10/sup -5/ to less than 10/sup -12/.     

Multigigabit multichannel optical interconnection module forbroadband switching system

This paper describes optical transmitter and receiver modules for package-to-package interconnection in broadband switching networks such as an asynchronous transfer mode switch fabric. These modules, which include the multiplexer and demultiplexer, can reduce the number of connections and the problem of skew between links. Five-channel optical transmitter and receiver modules were fabricated and demonstrated at 2.8 Gbit/s with a power dissipation of 4.5 W per channel. Moreover, temperature-insensitive optical interconnection was successfully demonstrated by driving a laser with a constant bias current over the threshold and by deducting the optical signal offset. The output power of the transmitter module was -4.2 dBm. Nonuniformity of the transmitter output powers across the range of optical channels was <2.1 dB. Receiver sensitivity for a bit error rate of 10^-11 was -9.3 dBm. Nonuniformity of the receiver sensitivities was <1.5 dB. The power penalty of the receiver sensitivity due to crosstalk was 1 dB. The connection distance was >250 m     

Low noise accelerometer microsystem with highly configurable capacitive interface

This paper presents a low noise accelerometer microsystem with a highly configurable capacitive interface circuit. A programmable capacitive readout circuit is designed to minimize the offset and gain error due to the parasitic capacitance mismatch and the process variations. The interface circuit is implemented in a 0.5 μm 2P3M CMOS technology with EEPROM. The interface circuit and MEMS sensing element are integrated in a single package, and consist the accelerometer microsystem. The supply voltage and supply current of the system are 5 V and 1.17 mA, respectively. The input range and gain are 2.5 V and 0.5 V/g, respectively. The max–min gain error and max–min offset error after calibration was measured to be 1.2% FSO and 3.3% FSO, respectively. The signal to noise ratio (SNR) and noise equivalent resolution (NER) are measured to be 93.1 dB and 110.6 μg/√Hz, respectively, when a 40 Hz, 5 g sinusoidal input acceleration is applied.     

Pulse width modulation for analog fiber-optic communications

The pulse width modulation (PWM) technique has been revisited and analyzed to evaluate its merits for application to analog signal transmission in fiber-optic links. Fourier analysis of the PWM signal reveals that it can be used as a vehicle to launch an analog signal onto optical fiber when a symmetrical natural sampling process is used. The SNR of the modulated signal depends on the timing jitter of the carrier pulses and a wide-band (45 MHz) SNR of 45 dB has been obtained with a commercially available multimode laser transmitter. A linear dynamic range of over 50 dB has been experimentally demonstrated. The full fiber bandwidth can be utilized by using a very high pulse carrier frequency, while a more popular pulse frequency modulation technique provides about a 10-MHz analog signal bandwidth when 1 km of multimode fiber is used in conjunction with a short wavelength (0.87 μm) LED transmitter. Analog transmission capability was experimentally demonstrated by constructing a simple video link using common laboratory equipment. The performance of the video link supports the PWM modulation theory developed here and elsewhere. The experimental results indicated that PWM is potentially very attractive for low-cost broad-band local area network (LAN) application, including future highly interactive offices, hospitals, and automated factory floors.     

DC-Coupled Burst-Mode Laser Diode Driver with Automatic Power Control for 1.25Gbit/s PON System

An integrated burst-mode laser diode driver is presented for PON application. The bias current range and modulation current range are 1–75 mA and 5–80 mA respectively. The DC-coupled interface between the driver and the laser diode can tolerate the output transient voltage as low as 0.6v. The novel digital APC loop can stabilize the output average optical power and extinction ratio respectively within ± 0.3 dBm and ± 0.4 dB (−40 to 100^∘C) with less than 0.6 μs initialization time and infinite bias current and modulation current hold time. Moreover, the fast burst response is achieved with burst on/off time less than 5 ns. The chip is implemented in a TSMC 0.35-μm SiGe BiCMOS technology and occupies an area of 1.56 × 1.67 mm² with power consumption of 105 mW from a supply voltage of 2.5 v.     

Statistics of Electrical Dispersion Compensator Penalties of 10-Gb/s Multimode Fiber Links With Offset Connectors

In this letter, we investigate the penalty after a 10-Gb/s Ethernet signal is detected and processed. We study the statistics of ideal electrical dispersion-compensation (EDC) performance, measured by the penalty of an ideal decision feedback equalizer (PIE-D), of 300-m multimode fiber links to determine the theoretically best possible EDC performance. We calculate the channel responses using two methods: the individual-mode method and the average-mode method. We find a strong dependence of the PIE-D value on the channel model that is used, especially when there is a connector with a large offset in the link. In system design, one should choose a suitable channel model, taking into account the length of the fiber, the magnitude of offset, and the percentage of coverage     

A technique for characterizing surface recombination in silicon wafers based on thermal-emission measurements

A noncontact technique for the measurement of the surface-recombination rate in silicon wafers is suggested. A wafer under study is excited optically in the spectral region of intrinsic absorption, and the excitation-wavelength dependence of the power of the wafer thermal emission beyond the intrinsic-absorption edge is examined. The surface-recombination rate is determined from the ratio of intensities of the wafer thermal emission in the wavelength range 3–5 μm recorded under excitation with two laser diodes with wavelengths of 863 and 966 nm. Wafers subjected to different surface treatments were tested; at 230°C, rates on the order of 10⁴ cm/s were measured after mechanical polishing and 10³ cm/s after etching in CP-4A etchant. The applicability of the method is discussed, and the measurement error as a function of the wafer and light-source parameters is considered.     

The effect of spurious intensity modulation in semiconductor diode lasers on the performance of optical heterodyne frequency shift-keyed communications systems

Analytical expressions are derived for the bit-error rate (BER) of anM-ary frequency shift-keyed (FSK), heterodyne, optical communication system with noncoherent demodulation in the presence of spurious intensity modulation (SIM) and frequency noise. The SIM degradation of an FSK system, implemented with semiconductor diode lasers, is estimated for lasers with zero and nonzero linewidths and will be discussed for a distributed feedback laser operating at 1.5μm and a channeled substrate planer laser operating at 0.83 μm. The SIM power penalty is typically less than 1 dB, but can exceed 1 dB for 2-, 4-, and 8-ary FSK at data rates above 1 Gbit/s.     

5 Gbit/s, 233 km optical fiber transmission experiment employingfive semiconductor laser amplifiers

A directly modulated 1.519-μm distributed-feedback laser signal was transmitted over 233 km of single-mode fiber consisting of dispersion shifted fiber and conventional step-index fiber to minimize the dispersion penalty. The power penalty after the transmission was 0.25 dB. The results show the effectiveness of an optical amplifier repeater system for high-speed long-haul fiber optic transmission     

Noise caused by semiconductor lasers in high-speed fiber-opticlinks

Theoretical and experimental results are presented for the signal-to-noise (S/N) ratio caused by mode partition noise, intensity noise, and reflection-induced noise in optical data links. Under given conditions an additional noise source with a S /N ratio of 20 dB will cause a power penalty of 1 dB in order to maintain a 10^-9 bit error rate. From numerical simulations the authors predict the maximum allowable dispersion in the presence of mode partition noise to be approximately 40% of a clock period. This figure is almost independent of bit rate and laser structure and agrees well with the measurements and with results of other workers. Numerical simulations of a buried-heterostructure and a TJS laser were carried out at four bit rates from 565 Mbit/s to 4.5 Gbit/s and the measurements were done at 2.2 Gbit/s using a TJS laser