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.     

Simultaneous single-fibre transmission of video and bidirectionalvoice/data using LiNbO3 guided-wave devices

A system experiment which uses integrated optics to effect bidirectional transmission on a single-mode fiber is described. The system has practical applications and provides more functionality than previously reported experimental systems. The system consists of a video link (180 Mbit/s) and a voice/data link (1.54 Mbit/s) to the end user and a return voice/data link (1.54 Mbit/s) from the end user. Two LiNbO ₃ devices are used to externally modulate lasers and a third is used in a novel way to demultiplex the incoming signals and to eliminate the need for an optical source at the user's end. The system operated over 4 km of standard single-mode fiber with a BER⩽10^-9 and excess margins (4.9, 9.3, and 28.1 dB) on the three links     

1.3 ?m bidirectional optical transmission over 31 km of installed single-mode fibre using optical couplers

Results are reported of 1.3 ?m bidirectional optical transmission over 31 km of installed cabled fibre at transmission rates of 34?650 Mbit/s using fused biconical tapered couplers manufactured at BTRL. With the introduction of 6 dB extra path loss it is possible to double the system capacity incurring only a small additional penalty at 34 and 140 Mbit/s and no other penalty at 320 and 650 Mbit/s.     

Subscriber loop transmission using low operating current light emitting diodes subjected to temperature extremes

A unique edge-emitting LED has been developed that has characteristics particularly attractive for use in loop transmission equipment. At low operating currents of 20-25 mA, sufficient optical power is launched into a Single-mode fiber to transmit data rates typical of the present day loop plant, 1.5-45 Mbit/s. In the system experiments reported here, 45-Mbit/s data was transmitted 12.9 km while operating the LED at a low drive current of 20-mA peak and at temperatures from -20 to +70°C. These experiments and related analyses confirm that the LED offers a reliable, low cost, and easy to use alternative to diode lasers and high drive current LED's in the telephone loop plant.     

High-capacity 1.3 ?m unrepeatered optical fibre transmission system trials for submarine applications

A series of high-capacity optical transmission system experiments at 1.3 ?m wavelength are reported. Margins greater than 2 dB were observed at 144 Mbit/s over 93 km and at 750 Mbit/s over 65 km, thus demonstrating the practicality of unrepeatered optical systems using commercially available components.     

Measurement of mode partition in DFB lasers

Some DFB (distributed feedback) laser diodes have a satellite mode beside a main DFB mode even if FP modes are suppressed. In this paper, the mode partition noise is presented for several DFB lasers operating in multilongitudinal modes. The results show that under modulation at 140 Mbit/s, the mode partition coefficient k²of multimode DFB lasers is very small and at most 0.02 while that of FP lasers biased at the threshold level is 0.03 to 0.12. The numerical evaluation of the mode partition effect in two-mode DFB lasers suggests that a 20- dB suppression of the satellite mode power is enough to achieve a repeater spacing of over 100 km in the 280 Mbit/s fiber-optic transmission system with less than 0.1-dB power penalty.     

Transmission experiments through 101 km and 84 km of single-mode fibre at 274 Mbit/s and 420 Mbit/s

Four transmission experiments through low-loss single-mode optical fibre at 1.3 ?m have been performed at 274 Mbit/s and 420 Mbit/s with different objectives. The first demonstrates transmission through 101 km of single-mode fibre at 274 Mbit/s with negligible dispersion penalty. The second experiment at 274 Mbit/s and 84 km uses only components suitable for use in an undersea cable system. Two additional experiments, both at 420 Mbit/s, accomplish a bitrate × distance product of 35 GHzkm with 84 km of fibre and show no dispersion penalty with 63 km and 2.4 ps/km nm dispersion.     

Two-section distributed feedback lasers for incoherent frequency-shift-keying transmission systems

Fabrication and performance characteristics of two-section distributed feedback lasers operating at 1.55 mu m are presented. Using this type of laser, a 622 Mbit/s incoherent frequency-shift-keying system over a 40 km fibre has been demonstrated with a receiver sensitivity of -41 dBm at a BER of 10/sup -9/.<>     

FSK heterodyne transmission experiments at 560 Mbit/s and 1 Gbit/s

Optical frequency-shift-keying (FSK) signals are obtained from directly modulated distributed feedback (DFB) semiconductor lasers. Experimental studies of the direct frequency modulation (FM) characteristics of the DFB lasers show a nonuniform FM response due to the competing effects of thermal modulation of the laser active region and carrier density modulation. Equalization of the signal current to the laser is employed to produce a flat FM response from 30 kHz to 1 GHz. Optical FSK transmission and heterodyne detection experiments at 560-Mbit/s and 1-Gbit/s are conducted at a wavelength of 1497 nm. Receiver sensitivities of -39 dBm at 560 Mbit/s and -37 dBm at 1 Gbit/s are obtained. Transmission through 100 km of single-mode fiber at 1 Gbit/s is achieved with no degradation in receiver sensitivity.     

Optical Fiber System Trials at 8 Mbits/s and 140 Mbits/s

This paper describes an optical fiber system developed at the British Post Office (BPO) Research Centre, Martlesham Heath, which provides telephone circuits in an 8 Mbit/s junction between the Centre and Ipswich Telephone Exchange via 13 km of BICC cable incorporating Corning fibers. In parallel, a 140 Mbit/s system operating over 8 km of cable has been demonstrated. The systems were constructed in accordance with standard BPO equipment practice and the cables were installed by local area staff in existing ducts.     

1.3 ?m/1.5 ?m bidirectional WDM optical-fibre transmission system experiment at 144 Mbit/s

Results are reported of a 1.3 ?m/1.5 ?m bidirectional WDM transmission system experiment operating at 144 Mbit/s over 58 km of cabled single-mode fibre. Regenerators used Bell Laboratories-developed 1.3 and 1.5 ?m InGaAsP semiconductor lasers, InGaAs PIN diodes, microwave monolithic amplifiers and optical bidirectional couplers.     

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).     

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 Fiber Transmission System Demonstration Over 32 km with Repeaters Data Rate Transparent Up to 2.3 Mbits/s

An initial optical fiber transmission system under development for Army long haul tactical communications is described and evaluated. The system interfaces with the 2.304 Mbit/s data input and output of an Army inventory multiplexer and its orderwire. The system includes transmitter and receiver end terminals, three data rate transparent repeaters, 8 km of graded index optical fiber, plus three optical attenuators and various optical connectors for simulating transmission up to 32 km. Long repeater spacing is achieved using low loss fiber, semiconductor lasers stabilized using optical feedback, and avalanche photodiodes. The system met all of the specified requirements and shows that optical fiber transmission systems have excellent prospects of meeting full military specifications. The versatility of data rate transparent repeaters is achievable even for transmission up to the 64 km distance desired for Army long haul tactical communications.     

1 Gbit/s transmission experiment over 101 km of single-mode fibre using a 1.55 ?m ridge guide C3 laser

Using a cleaved-coupled-cavity (C3) ridge guide laser which oscillates in a single longitudinal mode at 1.55 ?m wavelength, we report the first lightwave transmission experiment exploying single-frequency lasers at speeds above 500 Mbit/s. We have achieved digital transmission with a bit-error rate of 2 × 10?10 at 1.0 Gbit/s over 101 km of single-mode fibre. This represents a record for the length of unrepeatered optical transmission for bit rates greater than 500 Mbit/s. Evidence for an error-rate floor, presumably due to residual partition noise, is observed. No such floor was observed in an 84 km?1 Gbit/s experiment using the same C3 laser.     

量子密钥分发和经典光通信波分复用共纤传输研究

研究了量子密钥分发和经典光通信波分复用共纤传输的技术难点和可行性。基于系统重复频率 40 MHz的诱骗态相位编码BB84协议量子密钥分发设备,提出了3种量子信号与经典光信号的波分复用共纤传输方案：单纤双向CWDM共纤传输方案,复用1 550.12 nm波长量子信号、1 310 nm波长时钟信号以及正向1 590 nm波长100 Mbit/s速率光信号和反向1 610 nm波长100 Mbit/s速率光信号,光纤传输距离70 km下密钥成码率达到1.2 kbit/s;双纤双向CWDM共纤传输方案,复用1 550.12 nm波长量子信号、1 610 nm波长时钟信号以及1个波长的同向光信号在1 310 nm波长OOK光信号速率10 Gbit/s,光纤传输距离55 km下,密钥成码率达到1.58 kbit/s;双纤双向DWDM共纤传输方案,复用1 550.12 nm波长量子信号、1 610 nm波长时钟信号以及2个同向波长各自为1 551.72 nm和1 552.52 nm,并模拟100 Gbit/s相干光通信DP-QPSK信号接收功率,光纤传输距离70 km下,密钥成码率达到1.16 kbit/s。     

Measurement and prediction of digital radio performance on a long overwater path

The simultaneous field trial performance of 34 Mbit/s 4PSK, 2 × 34 Mbit/s 8PSK and 4 × 34 Mbit/s 16QAM digital radio systems over a 158 km overwater path in Australia is reported, and the measured outage performance is then used to derive propagation data, which in turn is used to predict performance using quadruple diversity. In addition, a generalised outage prediction technique is derived for n diversity.     

System experiments using 1.3 ?m LEDs

An experimental LED/PIN system is described that operates at 274 Mbit/s over 7.5 km or at 44.7 Mbit/s over 23.3 km without repeaters. These results are compared with repeater spans calculated for various loss and bandwidth conditions.     

Vertical cavity lasers for telecom applications

The authors review the development of long-wavelength vertical cavity lasers (VCLs) for telecommunications applications. Long-wavelength VCLs provide an attractive choice for inexpensive fiber optic communication. The different designs of such lasers are presented, along with the advantages and disadvantages of each. System requirements and experiments are also presented at 2.5 Gb/s over 200 km of optical fiber     

Low-loss dispersion-shifted single-mode fiber manufactured by the OVD process

The development of a low-loss dispersion-shifted single-mode fiber with a segmented-core profile is reported. The combination of low dispersion in the 1550-nm window, 0.21-dB/km median attenuation at 1550 nm, excellent bend resistance (lambda_{c} = 1200nm), and good splicing behavior make this fiber an economically viable alternative for long-haul high-data-rate operation utilizing multilongitudinal mode lasers. System experiments have demonstrated bit rates as high as 1.3 Gbit/s over 107 km and repeaterless spans of up to 233 km.