Search

In the active echo cancellation (AEC), the jammer can suppress the true target by superimposing on it a false target with the same amplitude and inverted phase. Under certain conditions, the interrupted-sampling repeater jammer (ISRJ) performs a kind of partial AEC against chirp radars. A novel technique that not only eliminates the effect of a self-protection ISRJ is proposed, but also the jamming signal power to augment the power of the true target is exploited. The theoretical analysis of this technique is presented and its effectiveness is verified by simulation.

The statistics of the delay spread in a two-path mobile radio environment where every path is subject to log-normal shadowing are derived. The channel profile thus considered consists of two delta functions whose power levels are in addition, correlated. Analytical expressions for the probability density function, the mean and the standard deviation of the resulting delay spread are obtained and compared with simulation results.

The intensity noise reduction capability of an all-optical 2R repeater using an injection-locked laser diode (ILL) is examined, and the effectiveness of the use of the repeater is verified in coherent CPFSK long-haul transmission experiments with in-line optical amplifiers.

The authors report 2.5 and 10 Gbit/s transoceanic distance transmission in a commercial FSA optical amplifier system which has 90 km repeater spacing. The unique fibre dispersion management technique and amplifier passband management scheme used in the system are successfully demonstrated. The SNR improvement achieved with polarisation scrambling is also reported.

The performance of 980 nm-pumped, two stage erbium-doped fibre amplifiers incorporating mid-amplifier components is investigated experimentally to determine their suitability as in-line repeaters for long haul soliton systems. Amplifiers are considered with counter-propagating pump and signal, as are devices pumped through WDMs located in the middle of the amplifier. These devices are found to offer significantly better noise performance than single stage designs.

Chromatic dispersion measurement is demonstrated on a 4564 km transmission system with 138 cascaded optical amplifiers. The technique uses a phase error cancellation method, which significantly reduces the phase error due to the system length fluctuations. It also uses temperature tuned DFB-LDs, which provide precise and stable probe wavelength control over a few nanometres.

In the deep sub-micron regime, the performance of network-on-chip (NoC) architectures is bound by the limited power and area budget. Proposed is a low-power low-area NoC architecture using a novel power-efficient control circuit that enables repeaters along the inter-router links to function as adaptive link buffers, thereby reducing the number of buffers required in the router. Simulation results in the 90 nm technology show power savings of nearly 45% and area savings of 50% for the proposed technique.

The increase in WDM transmission distance at zero-dispersion wavelength made possible by pre-compensation to offset nonlinear interchannel crosstalk is studied. A simulation shows that pre-compensation allows higher fibre launched power and increases the transmission distance by 3.3 times for a 50 GHz-spaced 8-channel WDM system. Pre-compensation is shown to be limited by the undeterministic nonlinear distortion induced by the accumulated amplifier spontaneous emission noise from repeater amplifiers. Also, optical power tolerance of the pre-distorted waveform generated at the transmitter is studied.

2.5 Tbit/s transmission of 12.5 GHz-spaced 256 ultra-dense wavelength-division-multiplexing (WDM) channels over a standard singlemode fibre of 2000 km with a repeater spacing of 100 km is presented. A non-return-to-zero modulation format and C-band erbium-doped fibre amplifiers are exclusively used. The results demonstrate the upgradability of conventional WDM transmission networks towards UD-WDM transmission networks.

The cascadability of fibre-to-the-premises systems with remote repeaters using a recirculating loop is experimentally investigated. The system employs standard PON transceivers and is demonstrated for four stages with

We report a new passive optical network (PON) architecture to reduce customer transmitter cost using an upstream repeater at the remote node. The system can further provide both downstream and upstream regeneration by utilising standard bidirectional transceivers. Our architecture can extend a conventional PON's feeder fibre reach to 50 km and split ratio to 1:256. The system demonstration shows insignificant penalty to the existing network performance and meets the IEEE 802.3ah standard requirements.

A bidirectional studio interconnection system operating at 10 Gbit/s over 123 km installed standard singlemode fibre is presented. Uncompressed HDTV programme channels are transmitted in STM-format without an in-line repeater, using the dispersion supported transmission (DST) method.

A 10 Gbit/s 10 channel transmission experiment with 100 km repeater spacing (23 dB fibre loss) is demonstrated with 600 km dispersion shifted fibre. Transmission was successfully performed by employing fluoride-based erbium doped fibre amplifiers and unequal channel spacing allocation.

WDM transmission over a 3711 km installed optically amplified submarine cable system is reported. They also show the implications of varying the repeater output power by means of a proprietary supervisory system resulting in optimised system performance.

5.3 Gbit/s 11300 km data transmission using actual submarine cables and EDFA repeaters with 60 km spacing has been successfully achieved. The measured value of Q/sup 2/=16.4 dB (corresponding to BER=2.1*10/sup -11/). This transmitted distance using the actual system is the longest reported to date, as far as the authors know.< >

A global fibre transmission experiment consisting of optically amplified electronic regenerators has been demonstrated for the first time transmitting 5 Gbit/s NRZ data with a extended span of > 200 km to a distance of 500 000 km.

The authors have demonstrated, for the first time, 10 Gbit/s transmission over 360 km of embedded standard fibre cables. During the five month long field experiment, the 1.55 µm, 10 Gbit/s IM/DD system showed long term ‘error free’ transmission (less than 10-16 BER) with an optical repeater spacing of 120 km (33 dB repeater span loss).

Long-span nonrepeatered transmission systems are quite attractive for constructing economical large-capacity networks because repeater facilities can be reduced. Erbium-doped fiber amplifiers (EDFAs) as power amplifiers and preamplifiers have dramatically enhanced transmission capabilities, especially repeater spacing.1,2 At high fiber-input powers, however, degradation caused by fiber nonlinear effects limit the repeater span.3

For the first time, forward error correction (FEC) was used to improve the performance of a 5 Gbit/s 6400 km erbium doped fibre amplifier based system. The performance of a transoceanic optically amplified system can be significantly improved by using FEC. The Q required to achieve satisfactory performance is at least 5dB less than that without FEC. This additional margin could also be used to relax system specifications such as repeater spacing. As an example, the repeater spacing of a transoceanic system could be increased by more than 20% with no degradation in transmission performance with the use of FEC. The system robustness to degradation is also strongly enhanced by using FEC. >

The optimum configuration for hybrid Raman/EDFA amplification in ultra-long-distance 40 Gbit/s WDM transmission using a dispersion-flattened fibre span is investigated. By optimising the Raman gain, 16/spl times/40 Gbit/s WDM transmission over 2000 km was achieved with 80 km repeater spacing.

3.08 Tbit/s (77/spl times/42.7 Gbit/s) WDM transmission over 200 km fibre with 100 km amplifier spacing and 100 GHz channel spacing is demonstrated. Error-free transmission of all 77 channels is achieved by employing dual C- and L-band hybrid Raman erbium-doped inline amplifiers, experimental low dispersion slope TrueWave fiber, and forward error correction.

The results from a 640 Gbit/s (40 Gbit/s/spl times/16 channel) dense WDM soliton transmission experiment over 1000 km with the use of a dispersion-managed transmission line are reported. The spectral efficiency was as high as 0.4 bit/Hz. The transmission line comprised conventional 1.3 /spl mu/m singlemode fibres and dispersion compensating fibres with dispersion slope compensation and a repeater span of 50 km.

A 20 Gbit/s optical time division multiplexed transmission system based on components and subsystems operating at not more than 5 GHz repetition rate is reported. Full BER measurements indicate a penalty of only 0.8 dB after transmission through 205 km of dispersion-shifted fibre. The penalty was mostly attributed to the accumulation of noise from erbium-doped fibre repeater amplifiers in the system. >

The authors demonstrate +11 dBm-per-channel 320 Gbit/s (8/spl times/ 40 Gbit/s) WDM transmission over a 367 km zero-dispersion-flattened transmission line with 120 km repeater spacing using a nonlinearity-tolerant carrier-suppressed return-to-zero format.

A simple reshaping and regenerating (2R) repeater that uses an EA modulator directly driven by a uni-travelling-carrier photodiode has been developed. An experiment showed that it had good 2R performance at 10 Gbit/s. The power penalty arising from the accumulated amplified spontaneous emission noise at a bit error rate of 10–9 was 2–3 dB lower than that of a 1R repeater.

Optical phase-sensitive amplifiers (PSAs) are promising circuit elements for expanding the regenerative repeater spacing of optical transmission systems. The authors demonstrate error-free operation of in-line PSAs with a 10 dB net gain by using an injection-locked pump with a compensation phase-locked loop.

The authors describe an approach for realising a single-channel 40 Gbit/s optical repeater system using InP-based HEMTs. A fundamental optical repeater circuit using the HEMT IC modules successfully demonstrates 40 Gbit/s, 300 km transmission.

The authors show the feasibility of a 10 Gbit/s eight-channel multi-repeater transmission system using 1.55 /spl mu/m dispersion shifted fibres. Transmission over 480 km with 120 km long repeater spacings is achieved using an orthogonal polarisation arrangement and bit-phase arranged RZ pulse format.

Transmission performance has been greatly improved by employing bit-synchronous phase modulation to source pulses in 20 Gbit/s soliton-based RZ transmission experiments. The tolerable window for both repeater output power and signal wavelength, for 9000 km transmission, was doubled with phase modulation.

The widest, seamless, 76 nm (1531–1607 nm) 3 dB gain-band bidirectional amplifier is realised by combining an erbium-doped fluoride fibre amplifier (1531–1562 nm) and a gain-flattened erbium-doped silicate fibre amplifier (1562–1607 nm) in a novel configuration of gain-band separation between upstream and downstream signals. Bidirectional 10-channel WDM transmission at 2.5 Gbit/s over a 250 km conventional singlemode fibre is successfully demonstrated using our amplifiers as two bidirectional repeaters.

The impact of the nonlinear effect, combined with group velocity dispersion, on cascaded amplifier transmission systems is clarified experimentally using a 10 Gbit/s transmission system. Based on the results, the optimum amplifier output power is presented as a function of amplifier spacing. 3000 km transmission is feasible at 10 Gbit/s if the spacing is 100 km.

A supervisory signal transmission scheme using amplified spontaneous emission (ASE) for optical repeater systems is proposed. The 10 000 km transmission or the supervisory signal was successfully demonstrated by using a recirculating fibre loop

For the first time, all-optical regeneration using a nonlinear fibre Sagnac interferometer switch (NSIS) and pump-probe walk-off is demonstrated. In the NSIS, all-optical regeneration including timing and amplitude restoration is performed by switching clock pulses with amplified input signals. Timing restoration is evaluated by performing error-rate measurements at 5 Gbit/s. >

A 2.5Gbit/s, 50km span straight line transmission over 10 000 km using 199 Er-doped fibre amplifiers was successfully demonstrated. The simultaneous transmission or supervisory control and response signals was also confirmed

A proposed modification to the component geometry of a fibre amplifier repeater which allows on on-board cable fault location facility to be incorporated is reported. The measurement technique, based on OTDR, allows cable breaks in the section of optical fibre between two fibre amplifier repeaters to be located. >

An optical fibre loop is used to simulate experimentally a transoceanic system employing optical amplifier repeaters. Propagation of a data pattern at 2.5 Gbit/s is demonstrated to 10,000 km. Pulse distortion due to the accumulation of nonlinear (Kerr) and dispersive effects was observed.

A novel circuit technique that provides wideband clock extraction for digital regenerative repeaters is described. The scheme employs a closed loop electronically tuned YIG filter than can be locked to the fundamental or harmonics of the extracted clock.

The nonlinear pulling and pushing effects between adjacent solitons have been observed for the first time in a 20 Gbit/s soliton transmission system at around 400 km. Erbium-doped fibre amplifiers were used as lumped amplifiers for fibre loss compensation. The maximum transmission distance at which the interaction was negligible was about 350 km for a pulse width of 18ps and a repeater spacing of 25 km.

A 20 Gbit/s optical soliton transmission over 200 km has been successfully achieved for the first time by using multiple erbium-doped fibre repeaters. The erbium-doped amplifiers are used as lumped amplifiers. The repeater spacing is 25 km and the soliton pulse width is 20 ps. The erbium-doped fibre amplifiers are pumped by InGaAsP laser diodes.

A field demonstration of two channel 622 Mbit/s DPSK and FSK coherent transmission over 200 km of installed terrestrial fibre and unrepeatered over 264 km of undersea fibre is reported. Diode-pumped erbium-doped fibre amplifiers were used as power boosters and multi-wavelength repeaters. The maximum launch power of the amplifiers was > + 15dBm and the amplifiers exhibited repeater gains of ˜30dB.

Reports a field demonstration of 622 Mbit/s DPSK and FSK coherent transmission over 200 km of installed single mode fibre. Diode-pumped erbium doped fibre amplifiers were used as both power amplifiers and repeaters. System loss budgets of more than 68 dB were achieved with an intermediate amplifier repeater gain of 16.5 dB. Both systems incorporated fully automated endless polarisation control.

A 2.4 Gbit/s, four WDM optical fibre transmission experiment over 459 km using six Er-doped fibre amplifiers in the 1.55 mu m wavelength region is presented. The results confirm the possibility of WDM multiple optical amplifier repeater transmission systems. >

A four channel direct detection FDM operating at 565 Mbit/s with a channel spacing of 12 GHz which achieves a receiver sensitivity of −40 dBm is reported. A laser preamplifier is used to overcome the optical processing loss of the channel selective filter.

The applications of Raman amplifiers as repeater amplifiers or post-transmitter amplifiers in a high-density WDM system are theoretically investigated. There exists an optimum pump power which results in maximum amplifier gain. The result shows that amplifier gains up to 50 dB and 20 dB are achievable for use as a repeater and a post-transmitter amplifier, respectively.

A nonrepeated fibre transmission experiment over 250 km is achieved at 1.8 Gb/s in a direct-detection repeater system using LD pumped Er3+-doped fibre amplifiers as pre and postamplifiers. Repeater gain of 50 dB is accomplished.

The performance of a 1500 nm optical repeater using a low-reflectivity (travelling-wave) semiconductor laser amplifier is reported. At 140 Mbit/s, a maximum fibre-to-fibre gain of 20 dB was measured. In a system experiment, a repeater gain of 18 dB was achieved, with a bit error rate of 10?9.

The concept of a flexible regenerator employing multiple frequency timing recovery is presented. Results are given for two possible types of multiple passband timing recovery filters?narrowband-narrowband and narrowband-wideband. In both cases, results show that the regenerator can be retimed using either passband without significant degradation due to the proximity and bandwidth of the redundant passband.

Optical solitons in 1.5μm dispersion-shifted optical fibres have been successfully amplified and transmitted over 30– 50 km with an Er3+-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 50mW.

Simple formulas are derived for evaluating the timing-jitter accumulation in a chain of regenerative repeaters for optical-fibre transmissions. The timing circuit in each repeater is modelled as a phase-locked loop. An example of the use of these formulas is reported with reference to a 140 Mbit/s transmission system.

A sea trial of a 1.3 μm, 400 Mbit/s undersea optical repeater1,2 connected with a 1.3 km-long undersea optical cable was conducted in Sagami Bay at about a 700 m depth in January 1981. Stable performance for the repeater was confirmed, as it withstood such external mechanical forces as heavy tension, water pressure, vibration, shock and extreme temperature change during laying and recovering.