1.6 Tbit/s (40 × 42.7 Gbit/s) WDM transmission over 2400 kmof fibre with 100 km dispersion-managed spans

Transmission of 40 × 42.7 Gbit/s WDM channels is demonstrated over 2400 km of fibre with 100 km amplifier spacing and 100 GHz channel spacing. Dispersion-managed fibre spans, carrier-suppressed return-to-zero modulation format and hybrid Raman/erbium-doped fibre inline amplifiers were employed to achieve a record 40 Gbit/s, WDM transmission distance with 100 km terrestrial span lengths     

459 km, 2.4 Gbit/s four wavelength multiplexing optical fibre transmission experiment using six Er-doped fibre amplifiers

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.<>     

40-Gb/s OTDM to 4×10 Gb/s WDM conversion in monolithic InPMach-Zehnder interferometer module

Transformation of high bit-rate optical time-domain multiplexed (OTDM) signals into a multitude of lower bit-rate wavelength-division-multiplexed (WDM) channels is demonstrated by means of a single monolithically integrated indium phosphide Mach-Zehnder interferometer with semiconductor optical amplifiers in its arms. Full demultiplexing of 10-Gb/s OTDM signals into 4×10-Gb/s WDM channels is demonstrated. Bit-error-rate penalties are below 1.5 dB for polarization independent signal conversion throughout the 1.55-μm wavelength range     

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.     

Highly Spectrally Efficient DWDM Transmission at 7.0 b/s/Hz Using 8 65.1-Gb/s Coherent PDM-OFDM

In this paper, we discuss the realization of wavelength-division multiplexing (WDM) transmission at high spectral efficiency. For this experiment, coherent polarization-division multiplexing--orthogonal frequency-division multiplexing (PDM-OFDM) is used as a modulation format. PDM-OFDM uses training symbols for channel estimation. This makes OFDM easily scalable to higher level modulation formats as channel estimation is realized with training symbols that are independent of the constellation size. Furthermore, because of its well-defined spectrum OFDM requires only a small guard band between WDM channels. The dependence of the number of OFDM subcarriers is investigated with respect to the interchannel linear crosstalk. At a constant data rate the number of OFDM subcarriers is estimated to achieve lower linear crosstalk in order to achieve higher spectral efficiency. We then experimentally demonstrate dense WDM (DWDM) transmission with 7.0-b/s/Hz net spectral efficiency using 8 $,times,$65.1-Gb/s coherent PDM-OFDM signals with 8-GHz WDM channel spacing utilizing 32-quadrature-amplitude-modulation subcarrier modulation. Successful transmission is achieved over 240 km standard single-mode fiber (SSMF) spans with hybrid erbium-doped fiber amplifiers/Raman amplification.      

Transmission performance analysis of 8/spl times/10 Gb/s WDM signals using cascaded SOAs due to signal wavelength displacement

We have analyzed the transmission performance of 8/spl times/10 Gb/s wavelength division multiplexing (WDM) signals due to crosstalk in cascaded conventional semiconductor optical amplifiers (SOAs). Using two different methods, the crosstalk over the whole gain bandwidth in SOAs is calculated to be 2-5 dB lower for the positive detuning. Then, transmission performance of 8/spl times/10 Gb/s WDM signals up to 6/spl times/40 km span in terms of receiver sensitivity is estimated over various transmission distances using cascaded SOAs for the positive signal wavelength displacement of 30, 40, and 50 nm. Especially for 50 nm detuning, transmission performances with and without using a reservoir channel are similar to each other. Our results suggest that SOAs can be used as an optical amplifier for displacement larger than 50 nm without using the reservoir channel.     

Demonstration of 9×200 Mbit/s wavelength division multiplexedtransmitter

A multifrequency laser capable of generating 200 Mbit/s data rates simultaneously at nine different wavelengths is demonstrated. The laser is based on the monolithic integration of a waveguide grating router with semiconductor optical amplifiers and thus provides automatic alignment of the optical channel wavelengths. This multifrequency laser may have important applications for local access WDM networks     

Theoretical investigation of 8 /spl times/ 10-Gb/s WDM signal transmission performance based on gain-equalized SOAs using backward Raman pumping at DCF

We have theoretically investigated 8 /spl times/ 10-Gb/s wavelength-division multiplexing (WDM) signal transmission characteristics based on semiconductor optical amplifiers (SOAs) with equalized gain using discrete Raman amplification (DRA). Gain equalization and low noise figures have been obtained by adjusting the backward Raman pumping power and wavelength at a dispersion compensating fiber (DCF) for each span. Bit-error-rate characteristics were calculated for 8 /spl times/ 10-Gb/s WDM signal transmission over 6 /spl times/ 40-km single-mode fiber (SMF) + DCF links with gain-equalized SOAs using DRAs at DCF. Approximately a 2.5-dB improvement of the receiver sensitivity was achieved by using SOAs and DRAs with optimized Raman pumping. One can easily upgrade the transmission length of a link based on SOAs with an appropriate backward pump laser at each DCF.     

Ultra-long distance wavelength-division-multiplexed solitontransmission using inhomogeneously broadened fiber amplifiers

The use of inhomogeneously broadened amplifiers for wavelength-division-multiplexed (WDM) optical soliton transmission is proposed. Dynamic gain equalization can be achieved through saturation, by adjustment of the time-averaged intensity of control lasers tuned between the WDM channels. The authors investigate numerically an example in which seven WDM channels at 2 Gb/s each are equalized using parameter values reasonable for germanosilicate core erbium-doped fibers     

Amplification of WDM signals in fiber-based optical parametric amplifiers

We demonstrate for the first time, experimentally, the performance of fiber-based optical parametric amplifiers in wavelength-division-multiplexed (WDM) applications. Both a 3 /spl times/ 10 Gb/s and a commercial 7 /spl times/ 2.5 Gb/s WDM system are investigated together with the parametric amplifier. Limitations due to pump depletion and four-wave mixing are quantified. Measurements showing the performance in terms of power penalty and gain versus input-output signal power are presented.     

A general and rigorous WDM receiver model targeting 10-40-Gb/schannel bit rates

We present a general and rigorously formulated dynamic receiver model aiming at 10-40-Gb/s wavelength division multiplexing (WDM) system design applications. A demultiplexing (DEMUX) characteristic with periodic transfer function has been treated in detail and it has been indicated how the model should be adjusted to take into consideration a general type of noise spectral density (NSD). The bit error ratio (BER) is evaluated accounting for the influence of non-Gaussian detected amplified spontaneous emission (ASE) noise, noise correlation between stochastic noise samples in the receiver, the gain and effective noise figure variation with wavelength of optical amplifiers, channel crosstalk, and intersymbol interference (ISI) effects caused by nonideal signal modulation, fiber dispersion, fiber nonlinearities, optical MUX, and DEMUX filtering and the impulse response of the electrical low-pass filter in the receiver. Also, the influence of shot and thermal noise is taken into account. Numerical results for the BER are presented considering a realistic 16-channel 10-Gb/s WDM system operating in the C-band using normal transmission fibers and including cascaded erbium-doped fiber amplifiers (EDFAs) with dispersion compensating fibers     

10 Gbit/s transmission by two channel WDM over a 908 km, sevenoptical amplifier line

Two channel wavelength division multiplexing (WDM) over a 908 km path with seven in-line erbium doped fibre amplifiers (EDFAs) is reported. At the 10 Gbit/s transmission level the line exhibited a good performance margin and significant robustness to simulated faults. To the authors' knowledge, this is the longest amplifier spacing reported in a system of this length at this line rate     

WDM/FDM star coupler with gain using fibre amplifiers

An efficient amplified WDM/FDM star coupler is proposed. The size of the coupler can be increased by a factor of m using m fibre amplifiers. Furthermore, the complexity and cost of the proposed scheme are less than those of other configurations.<>     

Semiconductor laser diode optical amplifiers/gates in photonicpacket switching

In this paper, we will describe how semiconductor laser diode optical amplifiers/gates can be used in the photonic packet switching systems based on wavelength division multiplexed (WDM) techniques. First, we show that cross-gain modulation (XGM) can be suppressed when the device is used in the transparent condition of the waveguide material even when the input signal power exceeds +18 dBm. We then discuss an appropriate encoding for the optical signal. Experimental results show that high bit rate Manchester-encoding enables the use of semiconductor laser diode optical amplifiers/gates in the gain condition as well as the transparent condition. Finally, a new photonic packet receiver which utilizes a semiconductor laser diode optical amplifier as a packet power equalizer is proposed. This receiver accepts 17 dB power fluctuation at nanosecond speed for 10 Gb/s Manchester-encoded signal     

Performance of Forward-Error Correction Code in 10-Gb/s RSOA-Based WDM PON

We investigate the performance of the forward-error correction (FEC) code for the 10-Gb/s wavelength-division- multiplexed passive optical network (WDM PON) implemented by using reflective semiconductor optical amplifiers (RSOAs) with extremely limited modulation bandwidth and the electronic equalizers to compensate for the degradations resulting from the use of such RSOAs. We show that the error occurrences in this network strongly depend on the bit pattern and the burst errors are likely to occur. Thus, it is important to use the FEC code capable of correcting the burst errors such as Reed–Solomon (RS) code. In addition, since a significant penalty can be induced by the increased line rate resulting from the use of the FEC code, it is necessary to find the optimum redundancy required to minimize the bit-error rate. We also evaluate the tolerance to the chromatic dispersion of the proposed 10-Gb/s WDM PON implemented by using the RS code with the optimum redundancy.      

Zero-loss polarisation-independent four-channel tunable opticalfilter in InGaAsP/InP

A multi-grading filter with polarisation-independent channel positions and integrated with two amplifiers has been fabricated in InGaAsP/InP. The four tunable Bragg gratings allow the selection of one out of four channels in a WDM system at 1.55 μm. A packaged device with no fibre-to-fibre loss and worst case crosstalk below -16 dB has been fabricated     

An integratable polarization-independent tunable filter for WDMsystems: the multigrating filter

After a review of the design principles, we present new experimental and theoretical results about the multigrating filter (MGF), a tunable channel selection filter for wavelength division multiplexed (WDM) transmission systems. Bit error rates mere measured at 2.5 Gb/s for single- and multichannel operation of a packaged polarization independent four-channel MGF with integrated amplifiers. The single-channel results are compared with theory. A monolithic tunable channel dropping component has also been fabricated by integrating two MGF's, a splitter, and amplifiers. Bit error rates measurements are presented for optical (at 2.5 Gb/s) and electrical on-chip (at 622 Mb/s) channel dropping in single- and multichannel operation     

WDM-POLSK Transmission Systems by Using Semiconductor Optical Amplifiers

The authors demonstrate the potential of using POLarization Shift Keying (POLSK) modulation format combined with semiconductor optical amplifiers (SOAs) in wavelength division multiplexing (WDM) transmission systems. The constant intensity of the POLSK modulation format allows for substantial removal of cross-gain-modulation impairments in SOAs so that practical amplifier spacing values (more than 100 km) are demonstrated in various different experimental configurations. Record WDM transmission experiments at 10 Gb/s by using SOA-based amplification are presented in short and medium reach system architectures using either single mode fiber or nonzero dispersion shifted fiber     

Gain transient control for wavelength division multiplexed access networks using semiconductor optical amplifiers

Gain transients can severely hamper the upstream network performance in wavelength division multiplexed (WDM) access networks featuring erbium doped fiber amplifiers (EDFAs) or Raman amplification. We experimentally demonstrate for the first time using 10 Gb/s fiber transmission bit error rate measurements how a near-saturated semiconductor optical amplifier (SOA) can be used to control these gain transients. An SOA is shown to reduce the penalty of transients originating in an EDFA from 2.3 dB to 0.2 dB for 10 Gb/s transmission over standard single mode fiber using a 2³¹–1 PRBS pattern. The results suggest that a single SOA integrated within a WDM receiver at the metro node could offer a convenient all-optical solution for upstream transient control in WDM access networks.     

Reduction of semiconductor laser amplifier induced distortion andcrosstalk for WDM systems using light injection

Semiconductor laser amplifiers cause both distortion and crosstalk in WDM systems due to gain saturation. A method using light injection is experimentally demonstrated to reduce distortion and crosstalk. In a two-channel experiment with a data rate of 2.5 Gbit/s, it is found that light injection can eliminate the BER floor due to distortion and crosstalk