Km Of Dispersion-shifted Fiber Research Articles

Distribution of time-energy entanglement over 100 km fiber using superconducting singlephoton detectors

In this letter, we report an experimental realization of distributing entangled photon pairs over 100 km of dispersion-shifted fiber. In the experiment, we used a periodically poled lithium niobate waveguide to generate the time-energy entanglement and superconducting single-photon detectors to detect the photon pairs after 100 km. We also demonstrate that the distributed photon pairs can still be useful for quantum key distribution and other quantum communication tasks.

Analysis of distributed temperature sensing based on Raman scattering using OTDR coding and discrete Raman amplification

The behaviour of distributed temperature sensors based on spontaneous Raman scattering and coded OTDR (optical time domain reflectometry) is studied both theoretically and experimentally; in particular a high performance scheme has been implemented using amplitude modulation according to Simplex coding, direct detection and additional use of lumped Raman amplification to further extend the sensing range. An efficient and cost-effective distributed temperature sensing system operating along 30 km of dispersion-shifted fibre with 17 m spatial resolution and 5 K temperature resolution is theoretically demonstrated and experimentally achieved using 255 bit Simplex coding and low-power commercially available laser diodes (80 mW CW power). Use of lumped Raman amplification to produce high-power coded pulses allows further 10 km distance enhancement, resulting in a total measurement range of 40 km.

Noise-figure limit of fiber-optical parametric amplifiers and wavelength converters: experimental investigation

Recent theoretical work predicts that the quantum-limited noise figure of a x(3)-based fiber-optical parametric amplifier operating as a phase-insensitive in-line amplifier or as a wavelength converter exceeds the standard 3-dB limit at high gain. The degradation of the noise figure is caused by the excess noise added by the unavoidable Raman gain and loss occurring at the signal and the converted wavelengths. We present detailed experimental evidence in support of this theory through measurements of the gain and noise-figure spectra for phase-insensitive parametric amplification and wavelength conversion in a continuous-wave amplifier made from 4.4 km of dispersion-shifted fiber. The theory is also extended to include the effect of distributed linear loss on the noise figure of such a long-length parametric amplifier and wavelength converter.

Polarization-Insensitive All-Optical Wavelength Conversion Using Dispersion-Shifted Fiber With a Fiber Bragg Grating and a Faraday Rotator Mirror

We demonstrate a simple technique for polarization-insensitive all-optical wavelength conversion based on four-wave mixing in dispersion-shifted fiber (DSF) with a fiber Bragg grating and a Faraday rotator mirror. The experimental residual polarization sensitivity is reduced from more than 22-2 dB with 4 km of DSF, and the power penalty incurred in wavelength conversion for 10-Gb/s nonreturn-to-zero data is less than 1 dB for a 20-nm conversion distance. Theoretically, this technique will have negligible polarization sensitivity when the propagation loss of the pump through the DSF approaches zero.

Super-dense WDM transmission of spectrum-sliced incoherent light for wide-area access network

This paper presents a detailed study on superdense wavelength-division multiplexing (WDM) transmission of spectrum-sliced incoherent light used for a wide-area access network. The transmission performance possible with this approach is evaluated numerically with regard to the following items: the transmission limit due to the chromatic dispersion, optimized signal-to-noise ratio design for the optical spectral width taking into account the adjacent-channel crosstalk, and the nonlinear effect generated by four-wave mixing at around the zero-dispersion wavelength. Superdense WDM transmission is also performed experimentally using 25-GHz channel-spaced, 15-GHz wide, up-to 156-Mb/s signals through up to 120 km of dispersion-shifted fiber.

Super-dense WDM transmission technology in the zero-dispersion region employing distributed Raman amplification

This paper describes a practical system design and the transmission performance of high-capacity super-dense-wavelength-division-multiplexing (SD-WDM) transmission in the zero-dispersion region employing distributed Raman amplification (DRA). By combining several semiconductor laser diodes (LDs) of different wavelengths, gain-flattened DRA can be achieved. We quantitatively clarify the relation between the pump power and the maximum input signal power that can be injected into a transmission fiber by taking into account gain saturation due to pump depletion. Based on these analytical results and computer simulations on transmission performance, an SD-WDM transmission experiment is conducted. By employing four-wavelength, backward-pumped DRA and forward-error correction, we successfully demonstrate 1-Tb/s (100 /spl times/ 10 Gb/s) SD-WDM transmission with 25-GHz channel spacing (0.4-b/s/Hz spectral efficiency) in the C-band (zero-dispersion region) over 4 /spl times/ 80 km of dispersion-shifted fiber. These results show that DRA is a powerful technology in realizing high-capacity SD-WDM transmission, particularly in the zero-dispersion region.

10-Gb/s agile wavelength conversion with nanosecond tuning times using a multisection widely tunable laser

Simultaneous wavelength conversion and high-speed wavelength switching has been demonstrated using a multisection grating-assisted coupler sampled reflector laser. A high-output extinction ratio (>20 dBm) over a 30-nm wavelength range was observed. The 10-Gb/s data was switched between different output wavelengths at a 2.5-Gb/s rate and transmitted over 50 km of dispersion-shifted fiber with a small measured power penalty (<2 dB).

Automatic dispersion equalisation using bit error rate monitoring in 40 Gbit/s optical transmission system

The authors describe an automatic dispersion equalisation system using bit error rate monitoring and demonstrate its equalisation capability over 100 km of dispersion-shifted fibre in a 40 Gbit/s transmission experiment.

Reduction of cross-gain modulation in the semiconductor optical amplifier by using wavelength modulated signal

A novel dual-input Mach-Zehnder modulator was used in conjunction with a wavelength modulation scheme to remove the cross-gain modulation in the semiconductor optical amplifier (SOA). Eight 10 Gb/s wavelength-division-multiplexed channels are transmitted over 75 km of dispersion-shifted fiber with a semiconductor optical amplifier as an in-line amplifier, with less than 1.5-dB penalty.

Layered optical thin-film allpass dispersion equaliser for compensation of dispersion slope of optical fibres

The authors propose and demonstrate novel coupled two-cavity allpass filters realised entirely as thin-film structures for dispersion slope compensation of optical fibres. The filters have centre wavelengths tunable over 15 nm. By cascading two such filters, the dispersion slope can be adjusted between –4.5 and –12.0 ps3 over a compensation bandwidth between 2.4 and 1.2 nm, respectively. A combination of two of the cascaded filters enables transmission of 1.6 ps pulse trains at 1550 nm through 60 km of dispersion-shifted fibre without waveform distortion.

Performance degradation of long-distance optical WDM networks due to bandwidth limitations of wavelength multiplexers and demultiplexers

The characteristics of an optical signal passing though optical add/drop multiplexing (ADM) devices, which mainly consist of optical (de) multiplexers, are experimentally evaluated through 10 Gb/s/spl times/8-channel dispersion-managed wavelength-division multiplexing (WDM) transmission over 4000 km of dispersion-shifted fiber (DSF). A novel recirculating loop configuration is used to change the insertion positions and intervals of the ADM devices. Inserting a single ADM device near the receiver causes more electrical signal-to-noise ratio (SNR) degradation than if inserted near the transmitter. Periodically inserting ADM devices at small intervals into the transmission line also causes significant SNR degradation, The SNR degradation is sensitive to optical signal wavelength detuning. The resulting SNR degradation basically arises from the bandwidth limitations of the wavelength (de)multiplexers, and is exacerbated in long-distance transmission by the optical signal spectral broadening due to fiber nonlinearity.

Transmission of 4 x 2.5-Gb/s spectrum-sliced incoherent light channels over 240 km of dispersion-shifted fiber with 200-GHz channel spacing

We demonstrate a transmission of 4/spl times/2.5-Gb/s spectrum-sliced incoherent wavelength-division-multiplexed channels over 240 km of dispersion-shifted fiber. The channel bandwidth and the channel spacing are kept small using the intrachannel four-wave mixing at the receiver. The error-floor level is close to 1/spl times/10/sup -11/ and the dispersion penalty is within 1 dB at 1/spl times/10/sup -9/ bit-error rate. Eye opening simulation shows that incoherent channels are less sensitive to the fiber four-wave mixing than coherent channels.

50 GHz spaced, 32 × 10 Gbit/s dense WDM transmission in zero-dispersion region over 640 km of dispersion-shifted fibre with multiwavelength distributed Raman amplification

The authors present, for the first time, 32/spl times/10 Gbit/s transmission (50 GHz channel spacing) in the zero-dispersion region of dispersion-shifted fibre (DSF) by employing multiwavelength distributed Raman amplification. Each transmission span is bi-directionally pumped at two wavelengths, 1450 and 1465 nm, to construct a wideband distributed Raman amplifier. A hybrid amplifier formed by a gain-flattened erbium-doped fibre amplifier and a gain-flattened distributed Raman amplifier is used to successfully realise dense WDM transmission in the zero-dispersion region over 8/spl times/80 km of DSF.

3 Tbit/s (160 Gbit/s × 19 channel) optical TDM and WDM transmission experiment

A 3 Tbit/s (160 Gbit/s × 19 channels) optical signal has been successfully transmitted over 40 km of dispersion-shifted fibre. Low noise supercontinuum signal pulse sources and 70 nm bandwidth tellurite-based optical amplifiers are used for 3 Tbit/s signal generation and amplification.

Enhancement of power margin and scalability in WDM links adopting dispersion-shifted fibres using periodic-unequally-spaced-channel allocation

The authors transmitted 16/spl times/10 Gbit/s wavelength division multiplexed signals over 240 km of dispersion-shifted fibre using periodic-unequally-spaced-channel allocation. A similar power margin to that obtained using unequally-spaced-channel allocation (USCA) was obtained, with far greater channel number scalability than USCA.

Suppression of intensity noise in 10 Gbit/s spectrum-sliced incoherent light channel using gain-saturated semiconductor optical amplifiers

Two cascaded semiconductor optical amplifiers are used to suppress the intensity noise of a spectrum-sliced incoherent channel with a bit rate as high as 10 Gbit/s for 2.6 nm channel bandwidth. The incoherent channel is transmitted over 100 km of dispersion-shifted fibre with a negative transmission penalty caused by intra-channel four-wave mixing.

2.5 Gb/s transmission of a spectrum-sliced incoherent hight source with 0.92 nm bandwidth over 80 km of dispersion-shifted fiber

We present a spectrum broadening technique to improve the signal-to-noise ratio of spectrum sliced incoherent light sources using the fiber four-wave mixing effect which occurs in a nonlinear loop mirror located at the receiver. The initial transmission channel bandwidth of 0.92 nm was increased to 1.62 nm in the nonlinear loop mirror at the optical receiver, which enhances the signal-to-noise ratio to a desired value. Using this technique, we have demonstrated the transmission of a 2.5 Gb/s NRZ signal with the 0.92 nm bandwidth through a 80 km dispersion-shifted fiber. The measured transmission penalty was less than 0.2 dB at <TEX>$1{\imes}10^{-10}$</TEX> BER.

Adaptive dispersion equalisation by detecting dispersion fluctuations using PM-AM conversion

A novel adaptive dispersion equalisation technique that detects and equalises dispersion fluctuations in transmission fibre during data transmission is proposed. This technique first detects dispersion fluctuations in the fibre by using the PM-AM conversion effect at a monitoring wavelength, and then tunes the data wavelength to equalise the fluctuation. This technique was tested by conducting a 40 Gbit/s, 8.5 ps pulse transmission experiment over 300 km of dispersion-shifted fibre, and was shown to suppress the sensitivity degradation to below 0.2 dB when the temperature of the fibre was varied between 0 and 40/spl deg/C.

3000 km transmission of densely-spaced, 2.5 Gbit s-1 directly-modulated channels demultiplexed with a concave grating demultiplexer

WDM transmission and demultiplexing of four directly-modulated DFB lasers at 2.5 Gbit s-1, with very narrow channel spacing (50 GHz) over 3000 km of dispersion-shifted fibre has been performed with a single-span recirculating loop test-bed. A high-performance free-space concave grating demultiplexer is used for the first time in a dense WDM transmission experiment.

Dispersion-compensation-free 16 × 10 Gbit/s WDM transmission in 1580 nm band over 640 km of dispersion-shifted fibre by employing optical duobinary coding

16-channel, 10 Gbit/s optical duobinary WDM signals in the 1580 nm band are successfully transmitted over 640 km (80 km /spl times/8) of dispersion-shifted fibre with no dispersion compensation or management.