Experimental Demonstration of Geometrically-Shaped Constellations Tailored to the Nonlinear Fibre Channel

A geometrically-shaped 256-QAM constellation, tailored to the nonlinear optical fibre channel, is experimentally demonstrated. The proposed constellation outperforms both uniform and AWGN-tailored 256-QAM, as it is designed to optimise the trade-off between shaping gain, nonlinearity and transceiver impairments

Simultaneous chromatic dispersion, polarization-mode-dispersion and OSNR monitoring at 40Gbit/s

A novel method for independent and simultaneous monitoring of chromatic dispersion ( CD), first-order PMD and OSNR in 40Gbit/s systems is proposed and demonstrated. This is performed using in-band tone monitoring of 5GHz, optically down-converted to a low intermediate-frequency (IF) of 10kHz. The measurement provides a large monitoring range with good accuracies for CD (4742 +/- 100ps/nm), differential group delay (DGD) (200 +/- 4ps) and OSNR (23 +/- 1dB), independently of the bit-rate. In addition, the use of electro-absorption modulators (EAM) for the simultaneous down-conversion of all channels and the use of low-speed detectors makes it cost effective for multi-channel operation. (C) 2008 Optical Society of Americ

Nanosecond channel-switching exact optical frequency synthesizer using an optical injection phase-locked loop (OIPLL)

Experimental results are reported on an optical frequency synthesizer for use in dynamic dense wavelength-division-multiplexing networks, based on a tuneable laser in an optical injection phase-locked loop for rapid wavelength locking. The source combines high stability (50 dB), narrow linewidth (10 MHz), and fast wavelength switching (<10 ns)

Digital dual-rate burst-mode receiver for 10G and 1G coexistence in optical access networks

A digital dual-rate burst-mode receiver, intended to support 10 and 1 Gb/s coexistence in optical access networks, is proposed and experimentally characterized. The receiver employs a standard DC-coupled photoreceiver followed by a 20 GS/s digitizer and the detection of the packet presence and line-rate is implemented in the digital domain. A polyphase, 2 samples-per-bit digital signal processing algorithm is then used for efficient clock and data recovery of the 10/1.25 Gb/s packets. The receiver performance is characterized in terms of sensitivity and dynamic range under burst-mode operation for 10/1.25 Gb/s intensity modulated data in terms of both the packet error rate (PER) and the payload bit error rate (pBER). The impact of packet preamble lengths of 16, 32, 48, and 64 bits, at 10 Gb/s, on the receiver performance is investigated. We show that there is a trade-off between pBER and PER that is limited by electrical noise and digitizer clipping at low and high received powers, respectively, and that a 16/2-bit preamble at 10/1.25 Gb/s is sufficient to reliably detect packets at both line-rates over a burst-to-burst dynamic range of 14,5dB with a sensitivity of -18.5dBm at 10 Gb/s. (C)2011 Optical Society of Americ

Corrections to "Replacing the soft-decision FEC limit paradigm in the design of optical communication systems"

Presents corrections to "Replacing the soft-decision FEC limit paradigm in the design of optical communication systems," (Alvarado, A., et al; (J. Lightw. Technol., vol. 33, no. 20, pp. 4338-4352, Oct. 2015)

Physical layer transmitter and routing optimization to maximize the traffic throughput of a nonlinear optical mesh network

This paper investigates the physical layer optimization as a means of improving the utilization of limited network resources. A transparent optical network operating in the nonlinear transmission regime using coherent optical technology is considered. A physical layer model is described that allows the transmission signal quality to be included in the optimization process. Initially a fixed power, route-adapted modulation format approach is taken using integer linear programming to solve the static route allocation problem. It is shown that for the 14-node, 21-link NSF mesh network adaptation of the modulation formats leads to increases in data throughput of 17%. Optimization of the individual transmitter launch powers and spectral channel allocation results in a SNR margin of 2.3 dB, which is used to further increase the overall network traffic throughput exceeding the fixed PM-QPSK modulation format by as much as 50%. Compared to other work this paper highlights that increased gains in network throughput can be achieved if nonlinear interference is included in the routing and spectral assignment algorithm and individual transmitter spectral assignment and launch power is optimized to minimize nonlinear interference

Achievable rate degradation of ultra-wideband coherent fiber communication systems due to stimulated Raman scattering

As the bandwidths of optical communication systems are increased to maximize channel capacity, the impact of stimulated Raman scattering (SRS) on the achievable information rates (AIR) in ultra-wideband coherent WDM systems becomes significant, and is investigated in this work, for the first time. By modifying the GN-model to account for SRS, it is possible to derive a closed-form expression that predicts the optical signal-to-noise ratio of all channels at the receiver for bandwidths of up to 15 THz, which is in excellent agreement with numerical calculations. It is shown that, with fixed modulation and coding rate, SRS leads to a drop of approximately 40% in achievable information rates for bandwidths higher than 15 THz. However, if adaptive modulation and coding rates are applied across the entire spectrum, this AIR reduction can be limited to only 10%

Digital back-propagation for nonlinearity mitigation in distributed Raman amplified links

The performance of digital back-propagation (DBP) for distributed Raman amplified optical communication systems is evaluated through analytical models and numerical simulations, and is compared with conventional lumped amplifier solutions, such as EDFA. The complexity of the DBP algorithm including the characteristic signal power profile of distributed Raman amplifiers is assessed. The use of full-field DBP in distributed Raman amplified systems leads to 1.3 dB additional gain with respect to systems employing lumped amplification, at the cost of only a 25% increase in complexity

Improved spectral characteristics of a single-mode semiconductor laser using a fibre grating and a reduced laser diode length

Use of a reduced laser diode length with a fibre Bragg reflector leads to decreased mode-hopping and a factor of 3 improvement in temperature stability of the lasing wavelength over Δ T=22°C. Single frequency output power of 1.7 mW in the fibre with 45 dB side mode suppression was obtained