Repeater spacing of 280 Mbit/s single-mode fiber-optic transmission system using 1.55 µm laser diode source

This paper describes an attainable repeater spacing for a high bit-rate single-mode fiber-optic transmission in the 1.55 μm wavelength region where laser mode partition noise comes to be significant. An expression for evaluating mode partition noise is given as the form involving the influence of laser spectral fluctuations under high bit-rate modulation, together with the intersymbol interference and the equalized pulse shape in tile optical receiver. After the validity of its numerical results is confirmed experimentally, the resulting evaluation of laser mode partition noise is connected to a systematic discussion on the attainable repeater spacing of a 280 Mbit/s fiber-optic transmission system operating at 1.55 μm, along with fiber loss versus dispersion tradeoffs. This discussion permits the attainable repeater spacing to be 60-70 km for the combination of a laser diode with 1.5-2.0 nm spectrum broadening and a fiber with the loss of 0.5 dB/km and the dispersion of 4-6 ps/km - nm.     

Long-span single-mode fiber transmission characteristics in long wavelength regions

Experimental and analytical results on high-speed optical pulse transmission characteristics for long-span single-mode fibers by using InGaAsP lasers, emitting at 1.1, 1.3, and 1.5 μm, as well as a Ge-APD are reported. At 1.1 μm, 400 Mbit/s transmission experiments were successfully carried out with 20 km repeater spacing. At 1.3 μm, where single-mode fiber dispersions approach zero, error rate characteristics showed that optical power penalties at 100 Mbits/s and 1.2 Gbits/s are negligible even after 30 and 23 km fiber transmission, respectively. It was confirmed that a 1.6 Gbit/s transmission system has 15 km repeater spacing. At 1.5 μm, where silica fibers have ultimately minimum loss, single-mode fiber transmission experiments were carried out at 100 Mbits/s with about 30 km repeater spacing. 400 Mbit/s transmission characteristics using 20 km fibers were also studied. Fiber bandwidths, measured by optical pulse broadenings after 20 km transmission, were 24, 140, and 37 GHz . km . nm at 1.1, 1.3, and 1.5 μm, respectively. Progress in lasers, fibers, and optical delay equalizers at 1.5μm will bring about large-capacity transmission systems having about 150 km repeater spacing. These results reveal fiber dispersion characteristics in the long wavelength region essential to high data rate single-mode fiber transmission system design.     

光纤通信用半导体激光器

半导体激光器是光纤通信用的主要光源,由于光纤通信系统具有不同的应用层次和结构,因而需要不同类型的半导体激光器。文章根据目前光纤通信系统的发展趋势,介绍几种典型的光纤通信用半导体激光器件———法布里-珀罗激光器、分布反馈半导体激光器、电吸收型调制器集成光源、波长可选择光源、垂直腔面发射激光器的特点和发展方向。     

Non-repeatered 50 km transmission experiment using low-loss optical fibres

An optical transmission experiment with an extremely long repeater spacing is conducted using graded-index multimode fibres, an InGaAsP/InP laser diode and a germanium avalanche photodiode A 53 3 km repeater spacing is realised by this experimental 1 27 ?m wavelength     

An Experimental 50 Mb/s Fiber Optic PCM Repeater

An experimental repeater for amplification and regeneration of 50 Mb/s fiber-optical pulses has been built and tested. For the receiver either Si p-i-n or avalanche photodiodes are used in conjunction with a high impedance FET input amplifier. The high voltage for the avalanche photodiode is generated internally and controlled by the received signal. This AGC circuit is capable of compensating for temperature changes of the avalanche gain over the range of-40 - +60degC. The optical transmitter consists of either a GaAs light emitting diode or a GaA1As laser diode coupled to optical fibers and directly modulated by a current driver with 30 percent electrical efficiency. For 10^-9error rate, the required average optical signal power for a pseudorandom signal is p-i-n diode: -41.5 dBm; avalanche diode: -56.6 dBm. The optical output power into a fiber with 1 percent index difference is LED: -17 dBm; GaAlAs laser: 0 dBm. The repeater power requirement is about 2 W.     

10-Gb/s, 4-channel wavelength division multiplexing fibertransmission using semiconductor optical amplifier modules

A dense wavelength-division-multiplexing (WDM) transmission system with very-high-speed channels was investigated experimentally. A 10-Gb/s four-channel WDM optical transmission (total capacity of 40 Gb/s) over a 40-km dispersion-shifted fiber was achieved by using hybrid-integrated DFB-LD/driver modules for transmitters and two cascaded semiconductor optical amplifier (SOA) modules for receivers. The experiment confirmed that the SOA is applicable for WDM transmission systems with high bit rates because of its inherent wide bandwidth. The transmission capacity of 40 Gb/s, achieved using an intensity modulation/direct detection (IM/DD) scheme, is the highest ever reported. This technology will make possible ultralarge capacity (up to several-hundred gigabits per second) and long-haul transmission systems in the future     

注入锁定法布里-珀罗激光器的单模工作特性

使用分布式反馈(DFB)激光器对法布里-珀罗(F-P)激光器进行单模注入锁定.通过改变F-P激光器的偏置电流,DFB激光器的输出功率以及两激光器间的波长失谐量,对注入锁定F-P激光器的光谱特性、功率特性以及频率响应特性进行实验分析.找出影响注入锁定F-P激光器稳定性的因素,并测量注入锁定F-P激光器的稳定锁定区;通过优化注人条件实现F-P激光器的高边模抑制比(SMSR)输出,最高可达55 dB;通过与自由运转F-P激光器比较,发现注入锁定可以明显抑制半导体激光器在高频调制下光谱的展宽.注入锁定后F-P激光器的3 dB调制带宽接近14 GHz.实验结果表明,通过合理设计光注入条件,注入锁定技术可以明显改善F-P激光器的光谱特性以及高频响应特性,并在高速光纤通信领域中得到广泛应用.     

Soliton amplification and transmission with Er/sup 3+/-doped fibre repeater pumped by GaInAsP diode

Optical solitons in 1.5 mu m dispersion-shifted optical fibres have been successfully amplified and transmitted over 30-50 km with an Er/sup 3+/-doped single-mode fibre repeater. The Er repeater was pumped by a GaInAsP Fabry-Perot-type, high-power laser diode, and a gain as high as 10 dB was obtained in the soliton power regime for an Er pump power of 50 mW.<>     

10 Gbit/s, 100 km optical fibre transmission experiment using high-speed MQW DFB-LD and back-illuminated GaInAs APD

The feasibility of 10 Gbit/s transmission has been confirmed through zero power-penalty transmission over a 100 km dispersion-shifted optical fibre employing a high-speed, small chirping MQW DFB-LD and a high quantum efficiency back-illuminated GaInAs APD.<>     

800 Mb/s fibre transmission test using low-loss and low-dispersion single-mode cable

Error-rate performances of a single-mode fibre transmission system are evaluated at wavelengths of 1.18 and 1.31 ?m. It is proven that longitudinal single-mode oscillation of the laser is important in a high-bit-rate system at a finite dispersion wavelength. At a low dispersion wavelength of 1.31 ?m, repeater spacing at 800 Mb/s was extended to 40 km, by developing a low-loss single-mode fibre cable, a stabilised optical transmitter and receiver and a single-mode optical connector.     

Dynamic optical soliton communication

Digitally coded optical solitons at 5 and 10 Gb/s have been successfully transmitted over 400 and 300 km, respectively, using erbium-doped fiber amplifiers and repeaters. The soliton pulse source is a gain-switched distributed-feedback laser diode with spectral windowing. The repeater spacing for the 10-Gb/s transmission with an input soliton of A=1.4 is 25 km, which is extended to 50 km for 5-Gb/s transmission with an input soliton of N=1.8-2.0     

Distributed feedback laser diode (DFB-LD) to single-mode fiber coupling module with optical isolator for high bit rate modulation

A distributed feedback laser diode (DFB-LD) module for single-mode fiber coupling is described in the 1.5-μm wavelength region. An optical isolator is constructed in the two lens coupling circuit to stabilize the DFB-LD characteristics. It consists of a DFB-LD as a polarizer, a yttrium iron garnet (YIG) plate and an analyzer. Coupling characteristics and attainable isolation of the proposed circuit have been studied theoretically and experimentally. The effect of reflected light on the DFB-LD characteristics such as relative intensity noise (RIN) and oscillation spectrum has been experimentally investigated taking into account the polarization of the reflected light. It has been clarified that the DFB-LD can function as an effective polarizer with an extinction ratio of more than 20 dB. The DFB-LD module was successfully fabricated to have stable spectrum characteristics and to sufficiently suppress the noise caused by reflections. It has been confirmed by a long haul transmission experiment that this module is applicable to large capacity optical fiber transmission systems.     

200-Mb/s/ch 100-m optical subsystem interconnections using8-channel 1.3-μm laser diode arrays and single-mode fiber arrays

Synchronous parallel optical-fiber transmission is an attractive method for providing increased interconnection throughput and higher density in advanced information systems. Skew suppression (reducing transmission delay time variation), error-free fully DC-coupled data transmission capability, compactness, and low power consumption of modules are important requirements. In order to meet these requirements, we developed optical subsystem interconnections using long-wavelength laser diode arrays and single-mode fiber arrays. The major design criteria are discussed, especially as they are related to skew due to laser diode turn-on delay and receiver input optical power variation. The use of low-threshold-current laser diode arrays is an important design requirement. Based on the design criteria discussed in this work, we demonstrated and channel 200-Mb/s/ch 100-m transmission using compact (0.18 cc/ch/module), low power (total 280 mW/ch), fully integrated transmitter and receiver modules with an ECL (emitter coupled logic) interface. These modules include our new laser diode arrays with low threshold current of 3.2 mA. Performance results showed that these modules are very effective as interconnections between synchronously operating subsystems     

Detailed evaluation of an attainable repeater spacing for fibre transmission at 1.3 ?m and 1.55 ?m wavelengths

An attainable repeater spacing at 1.3 ?m and 1.55 ?m wavelengths using a step-index monomode fibre cable is given, after detailed consideration of total loss as well as total dispersion of an optical fibre. The longest attainable repeater spacing at 1 Gb/s is about 100 km at 1.55 ?m wavelength using a single-mode laser diode and a monomode fibre with a relatively small core-cladding refractive index difference, e.g. about 0.2%.     

Demonstration of packet-by-packet wavelength conversion from FP-LDlight to ITU-T grid wavelengths

We demonstrated packet-by-packet wavelength conversion from Fabry-Perot laser diode (FP-LD) light to four ITU-T grid wavelengths. To achieve this we used a cross-phase modulation (XPM) wavelength converter and an arrayed-waveguide grating (AWG) router. Good feasibility was obtained at 2.5-Gb/s modulation. Selective wavelength conversion as described here is indispensable for the all-optical networks of future, in which optical signal sources without wavelength control will be used at user-end terminals     

Experimental demonstration of uncompressed 4K video transmission over directly modulated distributed feedback laser-based terahertz wireless link

We demonstrate the transmission of uncompressed 4K videos over the photonics-based terahertz (THz) wireless link using a directly modulated distributed feedback laser diode (DFB-LD). For optical heterodyne mixing and data modulation, a DFB-LD was employed and directly modulated with a 5.94-Gb/s non-return-to-zero signal, which is related to a 6G-serial digital interface standard to support ultra-high-definition video resolution. We derived the optimal frequency of the THz carrier by varying the wavelength difference between DFB-LD output and Tunable LD output in the THz signal transmitter to obtain the best transmission performances of the uncompressed 4K video signals. Furthermore, we exploited the negative laser-to-filter detuning for the adiabatic chirp management of the DFB-LD by the intentional discrepancy between the center wavelength of the optical band-pass filter and the output wavelength of the DFB-LD. With the help of the abovementioned methods, we successfully transmitted uncompressed 4K video signals over the 2.3-m wireless transmission distance without black frames induced by time synchronization error.     

High-speed optical pulse transmission at 1.29-µm wavelength using low-loss single-mode fibers

Optical-fiber transmission experiments in the 1.3-μm wavelength region are reported. GaInAsP/InP double-heterostructure semiconductor laser emitting at 1.293 μm is modulated directly in nonreturn-to-zero (NRZ) codes at digit rates tanging from 100 Mbit/s to 1.2 Gbit/s. Its output is transmitted through low-loss GeO2-doped single-mode silica fibers in 11-km lengths. Transmitted optical signals are detected by a high-speed Ge avalanche photodiode. Overall loss of the 11-km optical fibers, including 11 splices, is 15.5 dB at 1.3 μm. Average received optical power levels necessary for 10^-9error rate are -39.9 dBm at 100 Mbit/s and -29.1 dBm at 1.2 Gbit/s. In the present system configuration, the repeater spacing is limited by loss rather than dispersion. It seems feasible that a more than 30 km repeater spacing at 100 Mbit/s and a more than 20 km even at 1.2 Gbit/s can be realized with low-loss silica fiber cables, whose loss is less than 1 dB/km. Distinctive features and problems associated with this experimental system and constituent devices are discussed.     

Optical coherent broad-band transmission for long-haul anddistribution systems using subcarrier multiplexing

Signal multiplexing techniques for coherent optical transmission are compared, and appropriate application for a coherent subcarrier multiplexing (SCM) system is discussed. Optical frequency modulation (FM) using direct modulation of a distributed-feedback laser diode (DFB-LD) and a heterodyne detection is shown to be feasible. A transmission system using a local laser in the transmitter is unaffected by polarization and is cost effective. Phase noise can be suppressed by a phase-noise-canceling circuit (PNC) in a heterodyne receiver. This circuit can also effectively compensate for the frequency of instability of light sources. A theoretical simulation of a coherent SCM system showed that 100 channels of 30-MHz FM signal or 15 channels of 155-Mb/s signal can be distributed to 10000 subscribers using single-stage or double-stage optical amplifiers     

Power penalty due to optical back reflection in semiconductoroptical amplifier repeater systems

The effect of optical back-reflection on the bit-error-rate performance of a semiconductor laser amplifier repeater system is evaluated at 565 Mb/s. It is found that the degradation of the back-reflection is mainly caused by multiple reflection in the amplifier and depends on the internal gain of the optical amplifier and the reflectivity of the reflection points. It is concluded that in optical amplifier repeater systems with large gain, an optical isolator should be used to reduce the back-reflection penalty     

Bidirectional SCM Transmission Using a Noise-Suppressed Fabry–Pérot Laser Diode and a Reflective Semiconductor Optical Amplifier in a WDM/SCM-PON Link

We have proposed and experimentally demonstrated a bidirectional hybrid wavelength-division-multiplexed/subcarrier-multiplexed (SCM)-passive optical network based on a noise-suppressed Fabry-Peacuterot laser diode (FP-LD) and a reflective semiconductor optical amplifier (RSOA). For downlink data transmission, an FP-LD with multiple wavelength characteristics was used, and the mode partition noise of the FP-LD was reduced using a gain-saturated SOA with high-pass filter characteristics. For uplink data transmission, the downlink optical source was reused and remodulated by an SCM method, using an RSOA. A bidirectional SCM link with radio frequencies (RFs) of 2.4 GHz in the downlink and 1.0 GHz in the uplink was implemented. To confirm the validity of the proposed configuration, a 16-quadrature amplitude modulation transmission experiment was performed on a 10-km bidirectional optical access link. The transmission performance was investigated by means of the error vector magnitude and RF spectrum