Gigabit/s optical receiver sensitivity and zero-dispersion single-mode fiber transmission at 1.55 µm

High-speed pulse response and receiver sensitivity at 1.55 μm were measured at data rates ranging from 400 Mbits/s to 2 Gbits/s, in order to elucidate characteristics of a reach-through p+nn- Ge APD. The p+nn- Ge APD receiver provided a 2 Gbit/s received optical power level of -32.0 dBm at 1.55μm and a 10^-9error rate, which was 4 dB better than the receiving level with a p+n Ge APD. Detector performance at 1.3μm was also studied for comparison with performance at 1.55μm. Single-mode fibers, which have 0.54 dB/km loss and zero dispersion at 1.55μm, and an optical transmitter-receiver, whose repeater gain is 29.2 dB, have enabled 51.5 km fiber transmission at 2 Gbits/s. The transmission system used in this study has a data rate repeater-spacing product of 103 (Gbits/s) . km at 1.55μm. Optical pulse broadening and fiber dispersion were also studied, using 1.55 and 1.3μm dispersion-free fibers. Future repeater spacing prospects for PCM-IM single-mode fiber transmission systems are discussed based on these experimental results.     

Gigabit/s Optical Receiver Sensitivity and Zero-Dispersion Single-Mode Fiber Transmission at 1.55 µm

High-speed pulse response and receiver sensitivity at 1.55 µm were measured at data rates ranging from 400 Mbits/s to 2 Gbits/s, in order to elucidate characteristics of a reach-through p/sup +/nn/sup -/ Ge APD. The p/sup +/nn/sup -/ Ge APD receiver provided a 2 Gbit/s received optical power level of -32.0 dBm at 1.55 µm and a 10/sup -9/ error rate, which was 4 dB better than the receiving level with a p/sup +/n Ge APD. Detector performance at 1.3 µm was also studied for comparison with performance at 1.55 um. Single-mode fibers, which have 0.54 dB/km loss and zero dispersion at 1.55 µm, and an optical transmitter-receiver, whose repeater gain is 29.2 dB, have enabled 51.5 km fiber transmission at 2 Gbits/s. The transmission system used in this study has a data rate repeater-spacing product of 103 (Gbits/s) /spl dot/ km at 1.55 µm. Optical pulse broadening and fiber dispersion were also studied, using 1.55 and 1.3 µm dispersion free fibers. Future repeater spacing prospects for PCM-IM single-mode fiber transmission systems are discussed based on these experimental results.     

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.     

1.8 Gbit/s 65 km optical transmission experiment using a 1.478 ?m DFB laser and Ge APD receiver

A 1.8 Gbit/s optical transmission system trial has been conducted over 65 km of conventional monomode fibre using a 1.478 ?m DFB laser and p+n Ge APD receiver. Using a 215 ?1, NRZ, PRB test sequence, a long-term BER of 2×10?10 was achieved. Dispersive effects introduced a 1 dB penalty after 65 km transmission.     

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.     

2 Gbit/s and 2.4 Gbit/s optical transmission field trial over a 32 km installed route

High-speed optical data transmission at 2Gbit/s and 2.4 Gbit/s has been demonstrated for the first time over an installed fibre-optic cable. Error-free transmission with operating margins of 15.8 dB and 12 dB over 10?9 BER was achieved over a 32 km route. The systems featured a 1.5 ?m DFB laser, Ge APD transimpedance receivers and full regeneration.     

Proton implanted VCSEL's for 3 Gb/s data links

Transverse single-mode and multimode intensity modulated butt-coupled InGaAs vertical cavity surface emitting lasers (VCSEL)s are investigated as a light source for optical fiber communication systems. Data transmission at 3 Gb/s with a bit error rate (BER) of less than 10 ^-11 is reported for both 4.3 km of standard fiber, as well as 0.5 km of multimode graded-index fiber, 10-μm active diameter single-mode VCSELs are shown to have lower mode competition noise requiring 3 dB and 6 dB less power at the front end receiver at a BER of 10^-11 compared to 19-μm and 50-μm active diameter devices, respectively. In data transmission with multimode VCSELs, the dispersion penalty is lower than for single-mode sources since the noise at the receiver is mainly determined by transmitter-mode competition noise     

10 Gbit/s, 100 km nonrepeatered fibre transmission experiment using a high-sensitivity semiconductor optical preamplifier

10 Gbit/s, 100 km nonrepeated fibre transmission has been demonstrated using a high-sensitivity receiver with two-stage cascade-connected semiconductor optical amplifiers and a pin PD front end. The sensitivity and its improvement were -23.5 dBm and 12.2 dB respectively, resulting in the allowable span-loss of 24.5 dB.<>     

89 km 10 Gbit/s 1310 nm repeaterless transmission experiments usingdirect laser modulation and two SL-MQW laser preamplifiers with lowpolarization sensitivity

An unrepeatered 89 km 1310 mn 10 Gbit/s transmission experiment has been carried out for the first time employing an SL-MQW DFB laser diode and a high sensitivity optical front end with 1310 nm strained layer MQW optical amplifiers, enabling a total power budget of 35.8 dB. A record receiver sensitivity of -30.3 dBm at 10 Gbit/s @1310 nm has been demonstrated     

The fabrication and performance of long lengths of silica core fiber

Three hundred kilometers of single-mode fiber exhibiting median optical losses of 0.19 dB/km at 1.57 μm have been fabricated from preforms made by a high-rate Modified Chemical Vapor Deposition (MCVD) process. A new fiber design [1] was utilized which minimizes Rayleigh scattering loss by reducing the amount of dopants in the core. Milestone systems experiments incorporating this fiber have already demonstrated 420-Mbit transmission through 203 km [2], 2-Gbit transmission through 130 km [3], 1.37 Tbit km/s using 10 wavelength division multiplexed lasers [4], 4-Gbit through 102 km using a novel electronic multiplexer/demultiplexer [5], and 4 Gbit through 117 km using a Ti:LiNbO3external modulator [6]. Additionally, very low induced losses from hydrogen and radiation are reported.     

High-Speed CMI Optical Intraoffice Transmission System: Design and Performance

This paper presents the design and performance features of a successfully developed optical intraoffice transmission system operating at 100-400 Mbits/s. The keys to the commercial realization of this simple, highly reliable, and low-cost system are the employment of the 1.3 μm LED and graded-index multimode fiber. Additionally important, the system makes use of coded mark inversion (CMI) coding to ensure bit sequence independence (BSI) and good error-monitoring capability. Experimental results have clarified the optimum bandwidth of the low-pass filter at the receiver end and the commercially attainable transmission distance. Furthermore, an available system gain of 15.4 dB is demonstrated through 400 Mbit/s transmission experiments. This value enables transmission over distances in excess of 4 km through multimode fiber (900 MHzcdotpkm, 0.8 dB/km).     

Novel full-duplex SSB WDM-RoF system with SLM technique for decreasing PAPR

A novel full-duplex single-sideband (SSB) wavelength division multiplexing radio over fiber (WDM-RoF) system with selected mapping (SLM) technique for decreasing peak-to-average power ratio (PAPR) is proposed in this paper. At the central office (CO), the generated SSB signal carrying 10 Gbit/s 16-ary quadrature amplitude modulation orthogonal frequency division multiplexing (16QAM-OFDM) downstream signal with SLM technique is sent to the base station, and 60 GHz SSB optical signal carrying 10 Gbit/s 16QAM-OFDM upstream signal is sent back to CO utilizing the wavelength-reuse technology. Simulation results show the proposed method for PAPR reduction can effectively improve the sensitivity of receiver, and the power penalty of the 16QAM-OFDM downlink (uplink) signal is about 2 dB (3 dB) at BER of 1×10-3 after 42 km standard single-mode fiber (SSMF) transmission.     

10-Gb/s strained MQW DFB-LD transmitter module and superlattice APDreceiver module using GaAs MESFET IC's

This paper describes the design and performance of a 10-Gb/s laser diode (LD) transmitter and avalanche photodiode (APD) receiver, both of which are based on GaAs MESFET IC's. The LD transmitter consists of a strained MQW distributed-feedback LD and one chip LD driver IC. The module output power is +4.6 dBm at 10 Gb/s. The APD receiver consists of an InGaAsP/InAl/As superlattice-APD and an IC-preamplifier with the 10-Gb/s receiver sensitivity of -27.4 dBm. As for the LD transmitter, we discuss the optimum impedance-matching design from the viewpoint of high-speed interconnection between LD and driver IC's. As for the APD receiver, the key issue is input impedance design of preamplifier IC, considering noise and bandwidth characteristics. Total performance of the transmitter and receiver is verified by a 10-Gb/s transmission experiment and a penalty-free 10-Gb/s fiber-optic link over 80 km of conventional single-mode fiber is successfully achieved     

Germanium reachthrough avalanche photodiodes for optical communication systems at 1.55-µm wavelength region

Germanium reachthrough avalanche photodiodes (Ge RAPD's) with high-frequency response have been designed, fabricated, and tested. In the calculation of frequency response, optimum depletion layer width of 21 µm has been found for 1.55-µm wavelength with the highest cutoff frequency of 830 MHz. The diodes fabricated by this design showed frequency degradation of less than 2 dB at 500 MHz and at 1.55 µm. This response has been unchanged up to 1.58 µm, indicating useful spectral limit lies at more than 1.58 µm. The diodes exhibited quantum efficiency of 80 percent and excess noise factor of 6.1 at a multiplication of 10 both for 1.55 µm. The breakdown voltage was 60- 90 v. The sensitivity of the diodes was measured at 100 Mb/s and 1.55 µm. The minimum detectable power of -44.3 dBm which is by 5.2 dB better than the conventional p⁺-n Ge APD has been achieved for 10^-11error rate. Comparison with InGaAs APD and p-i-n/FET receiver has been made by calculating minimum detectable power of RAPD at 500 Mb/s. Calculated sensitivity of RAPD is 1-2 dB worse than InGaAS APD and comparable to that of InGaAs p-i-n/FET receiver estimated from the reported experimental results.     

1.6 Gbit/s optical receiver at 1.3 ?m with SAW timing retrieval circuit

The performance of a 1.6 Gbit/s optical receiver employing a s.a.w. filter as a timing tank is reported. The error-rate characteristics in a p.c.m. transmission system using a 1.3 ?m In-GaAsP laser and single-mode fibres were studied. The average received optical power at a 10?9 error rate was ?28 dBm. In a 15 km transmission experiment, the receiving level was degraded by 2 dB owing to fibre dispersion. Timing phase margin of 75 degrees after 12 km transmission was confined with the self-timed receiver.     

Optical Fiber Submarine Cable System Development at KDD

An optical fiber submarine cable system using longwavelength and single-mode optical fiber is expected to provide economical long-haul digital transmission. This paper describes the recent research and development on an optical fiber submarine cable system for international communication at the KDD Research and Development Laboratories. An experimental model including cable and repeaters has been designed and manufactured. An experimental repeater of 1.3 μm and 280 Mbits/s was laid at a depth of 1500 m and its fundamental performance was measured in November 1981. Test production of longlength cable having a single continuous length of 30 km became possible in the end of 1981. In early June 1982, the experimental system with a 50 km cable length and two repeaters operating at 300 Mbits/s and 1.3 μm wavelength was laid in a loop into the Sagami Bay from the KDD Ninomiya Submarine Cable Landing Station.     

Long-distance gigabit-range optical fiber transmission experiments employing DFB-LD's and InGaAs-APD's

High-speed and long-distance transmission characteristics have been examined at 1.2, 2, and 4 Gbit/s, employing mesa structure DFB-DC-PBH LD transmitters and planar InGaAs APD receivers. High receiver sensitivities, -40 dBm at 1.2 Gbit/s, -37.4 dBm at 2 Gbit/s and -32.4 dBm at 4 Gbit/s, have been obtained employing high-speed and low noise InGaAs APD/FET receiver circuits. Long-span transmissions, 1.2-Gbit/s 170-km, 2-Gbit/s 141-km, and 4- Gbit/s 120-km at 1.55 μm, and 4-Gbit/s 74-km at 1.3 μm, have been performed. Power penalties caused by the LD wavelength chirping in the 1.5- μm wavelength region and error rate flooring caused by the LD side-mode oscillation in the 1.3- μm wavelength region are discussed. The transmission length is limited not only by the DFB LD wavelength chirping but also by the two-mode oscillation, which was observed at the pulse leading edge when LD bias current was near the threshold current. From the 1.3 μm wavelength 4-Gbit/s experiment, it was found that the pattern effect of the side-mode oscillation caused the error rate floor, when the LD bias current is set near the threshold current, and that the error rate floor disappeared when the bias current is set slightly above the threshold.     

10 Gbit/s optical front end using Si-bipolar preamplifier IC, flipchip APD, and slant-end fibre

An optical front end for a 10 Gbit/s optical receiver has been fabricated that features a 10 GHz Si preamplifier IC, a flipchip APD with an 80 GHz gain-bandwidth product, and slant-end fibre optical coupling. Hybrid construction consisting of a flipchip APD mounted directly on the preamplifier chip minimises interconnect parasitics, and slant-end fibre optical coupling simplifies flat-package assembly of chip and fibre. An optical sensitivity of -23 dBm was achieved.<>     

Long-span optical transmission experiment over 222.8 km of commercial monomode fibre at 140 Mbit/s and 1.525 ?m

A 140 Mbit/s optical transmission experiment has been conducted over 222.8 km of commercially available monomode, step-index fibre using a 1.525 ?m ridge-waveguide DFB laser and hybrid Ge APD receiver. An overall system margin of 1.2 dB was observed after full regeneration.     

GaAs integrated circuits for error-rate measurement in high-speed digital transmission systems

A high-speed GaAs MSI PRBS generator and an error detector have been built, tested, and applied to bit-error ratio measurements in a fiber-optic transmission link. The generator produces a 1023 bit sequence at 2 Gbit/s data rate. The detector compares, bit-by-bit, the input data with a locally regenerated sequence. With a 2 GHz clock, the direct-coupled generator/detector combination, without an optical link, exhibits less than one error in 10/SUP 14/ clock cycles. The complete fiber-optic link test system incorporates a 1 km multimode fiber, operates at 1.9 Gbits/s, and exhibits a bit-error ratio below 10/SUP -12/.