In-line Repeaters Research Articles

30.7 Tb/s Transmission over 400 km using 40 WDM channels of DP-16 QAM and Raman amplification without inline repeaters

Forty wavelength-division multiplexing (WDM) channels of 96 Gbaud (768 Gb/s) were transmitted over 400 km of SMF using only a Raman amplifier, which was accomplished through numerical simulations. Each WDM channel comprised eight electrical subcarriers of single sideband Nyquist-pulse-shaping. 16 quadrature amplitude modulation and dual polarization modulation were applied to each subcarrier channel and so one data symbol carried eight bits. The roll-off factor in the optical subcarrier spectrum was investigated from 2% to 11%, and the change in roll-off was analyzed according to the subcarrier channel in a single WDM channel. The spectral linewidth of the light source in the transmitter was changed up to 10 MHz, and the effect on the performance was examined for a coherent transmission system with constellation analysis. The optical input power per WDM channel was optimized and the wavelength spacing between WDM channels were analyzed using nonlinear effects from adjacent WDM channels. A transmission experiment for total 30.7 Tb/s over 400 km was performed using the obtained optimal values. BER evaluation was achieved by DSP algorithms including Kramers–Kronig detection and Nyquist filtering. All 40 WDM channels exhibited sufficient transmission performance using only the Raman backward pumping of the four pump wavelengths. The proposed system can be applied to unrepeatered metro‐networks or data-center interconnects.

Ultra-long-distance (>160 km) distributed optic fiber vibration sensing system without an in-line repeater.

We proposed a distributed optic fiber vibration sensing system that can realize a sensing distance of more than 160km without a repeater. The system's optical structure is based on the Mach-Zehnder and Sagnac hybrid interference technique. To increase the monitoring distance, we used a reflective erbium-doped fiber amplifier (EDFA) instead of a traditional reflector at the end of the sensing system. In addition, a phase-generated carrier was applied to eliminate the parasitic interferometric effects of Rayleigh scattering.

Experimental demonstration of the OQAM-OFDM-based wavelength stacked passive optical networks

We demonstrate a wavelength stacked passive optical network (PON) with offset quadrature amplitude modulation based orthogonal frequency division multiplexing (OQAM-OFDM), which can provide 100-km single mode fiber (SMF) transmission without any inline repeater amplifier for both downlink and uplink. By experiment, we verify the feasibility of this proposed PON system for bi-directional long distance transmission especially for asynchronous upstream. Experimental result shows that, negligible power penalty is achieved even with 100-km SMF transmission, and ~3.6-dB sensitivity improvement is obtained when compared to OFDM-based asynchronous system. Besides, the performance in terms of side-lode suppression and peak to average power ratio (PAPR) are also contrastively analyzed between OFDM and OQAM-OFDM-based PON system.

Investigation of the optical gain and noise figure for multi-channel amplification in EDFA under optimized pump condition

We present the results of an investigation of optical gain and noise figure for simultaneous multi-channel amplification of an erbium doped fibre amplifier (EDFA) under optimized pump condition. Different pump configurations with varying input signal levels show interesting features on gain flatness. In the experiment, population inversion along the fibre length which determines the gain-spectra and noise characteristics of the amplifier is adjusted through optimized fibre length and injected pump power in order to minimize the gain-tilt at C-band. It is observed that bi-directional pumping manifests the best combination of low noise and high gain of EDFA which are useful as in-line repeaters in WDM network. We obtain 30 ± 1.5 dB intrinsically flat small signal gain from 1538 nm to 1558 nm band of wavelength with noise figure <4 dB for 16-channel simultaneous amplification in a single stage EDFA without gain flattening filter.

Effects of the Optical Filter Bandwidth on the Transmission Performances of In-line Repeater Optical Amplifiers

A novel analytical expression for the system power budget vs. amplifier input power including the effects of the optical filter bandwidth is derived in this paper. The effectiveness of the model is demonstrated by performing transmission experiments.

10 Gbit/s dispersion supported transmission field trial over 123 km standard singlemode fibre for HDTV studio interconnection

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.

Two-stage erbium-doped fibre amplifiers suitable for use in long-haul soliton systems

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.

Effects of stray reflections on the performance of semiconductor laser amplifiers as in-line optical repeaters

The effects of stray reflections from the ends of optical fibres on the gain and spontaneous emission of a semiconductor laser amplifier have been analysed. The transfer matrix method (TMM) has been applied to give efficient solutions to the problem. The theoretical results show that these stray reflections can seriously deteriorate the performance of a single amplifier and can degrade the overall performance of a system incorporating a cascaded chain of amplifiers as in-line repeaters.

An investigation of the noise figure and conversion efficiency of 0.98 mu m pumped erbium-doped fiber amplifiers under saturated conditions

The results of an investigation of the noise figure and conversion efficiency or erbium-doped fiber amplifiers for unsaturated, moderately saturated, and heavily saturated operation are reported. Quantum-limited 3 dB noise figures result only for small signal operation of low-gain amplifiers. For high gain, partially saturated amplifiers useful as in-line repeaters, bidirectional pumping results in the best combination of noise performance and conversion efficiency while co-propagation of signal and pump produces the best noise performance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Laser diode pumped Er/sup 3+/-doped fiber amplifier in a 565 Mbit/s DPSK coherent transmission experiment

A laser-diode-pumped erbium-doped fiber amplifier, exhibiting 9-dB gain, has been operated as an in-line optical repeater in a 565-Mb/s coherent optical communications system. A sensitivity penalty of 0.4 dB was observed when the amplifier was positioned 35 dB away from the receiver, thus indicating a system improvement of 8.6 dB. By progressively reducing the coupling loss between amplifier and receiver, the noise figure of the contradirectionally pumped amplifier was calculated to be 5.4 dB, a value which is consistent with simple noise theory. >