31 research outputs found
Throughput gains from adaptive transceivers in nonlinear elastic optical networks
In this paper, we link the throughput gains, due to transceiver adaptation, in a point-to-point transmission link to the expected gains in a mesh network. We calculate the maximum network throughput for a given topology as we vary the length scale. We show that the expected gain in the network throughput due to transceiver adaptation is equivalent to the gain in a point-to-point link with a length equal to the mean length of the optical paths across the minimum network cut. We also consider upper and lower bounds on the variation of the gain in the network throughput due to transceiver adaptation, where integer-constrained channel bandwidth assignment and quantized adaptations are considered. This bounds the variability of results that can be expected and indicates why some networks can give apparently optimistic or pessimistic results. We confirm the results of previous authors that show finer quantization steps in the adaptive control lead to an increase in the throughput since the mean loss of throughput per transceiver is reduced. Finally, we consider the likely network advantage of digital nonlinear mitigation and show that a significant tradeoff occurs between the increase in the signal-to-noise ratio for larger mitigation bandwidths and the loss of throughput when routing fewer large-bandwidth superchannels
Throughput gains from adaptive transceivers in nonlinear elastic optical networks
In this paper, we link the throughput gains, due to transceiver adaptation, in a point-to-point transmission link to the expected gains in a mesh network. We calculate the maximum network throughput for a given topology as we vary the length scale. We show that the expected gain in the network throughput due to transceiver adaptation is equivalent to the gain in a point-to-point link with a length equal to the mean length of the optical paths across the minimum network cut. We also consider upper and lower bounds on the variation of the gain in the network throughput due to transceiver adaptation, where integer-constrained channel bandwidth assignment and quantized adaptations are considered. This bounds the variability of results that can be expected and indicates why some networks can give apparently optimistic or pessimistic results. We confirm the results of previous authors that show finer quantization steps in the adaptive control lead to an increase in the throughput since the mean loss of throughput per transceiver is reduced. Finally, we consider the likely network advantage of digital nonlinear mitigation and show that a significant tradeoff occurs between the increase in the signal-to-noise ratio for larger mitigation bandwidths and the loss of throughput when routing fewer large-bandwidth superchannels
The benefit of split nonlinearity compensation for single-channel optical fiber communications
In this Letter we analyze the benefit of digital compensation of fiber nonlinearity, where the digital signal processing is divided between the transmitter and receiver. The application of the Gaussian noise model indicates that, where there are two or more spans, it is always beneficial to split the nonlinearity compensation. The theory is verified via numerical simulations, investigating transmission of single channel 50 GBd polarization division multiplexed 256-ary quadrature amplitude modulation over 100 km standard single mode fiber spans, using lumped amplification. For this case, the additional increase in mutual information achieved over transmitter- or receiver-side nonlinearity compensation is approximately 1 bit for distances greater than 2000 km. Further, it is shown, theoretically, that the SNR gain for long distances and high bandwidth transmission is 1.5 dB versus transmitter- or receiver-based nonlinearity compensation
Why compensating fibre nonlinearity will never meet capacity demands
Current research efforts are focussed on overcoming the apparent limits of communication in single mode optical fibre resulting from distortion due to fibre nonlinearity. It has been experimentally demonstrated that this Kerr nonlinearity limit is not a fundamental limit; thus it is pertinent to review where the fundamental limits of optical communications lie, and direct future research on this basis. This paper details recently presented results. The work herein briefly reviews the intrinsic limits of optical communication over standard single mode optical fibre (SMF), and shows that the empirical limits of silica fibre power handling and transceiver design both introduce a practical upper bound to the capacity of communication using SMF, on the order of 1 Pbit/s. Transmission rates exceeding 1 Pbit/s are shown to be possible, however, with currently available optical fibres, attempts to transmit beyond this rate by simply increasing optical power will lead to an asymptotically zero fractional increase in capacity
Real time dynamic strain monitoring of optical links using the backreflection of live PSK data
A major cause of faults in optical communication links is related to unintentional
third party intrusions (normally related to civil/agricultural works) causing fiber breaks or
cable damage. These intrusions could be anticipated and avoided by monitoring the dynamic
strain recorded along the cable. In this work, a novel technique is proposed to implement realtime
distributed strain sensing in parallel with an operating optical communication channel.
The technique relies on monitoring the Rayleigh backscattered light from optical
communication data transmitted using standard modulation formats. The system is treated as a
phase-sensitive OTDR (ΦOTDR) using random and non-periodical non-return-to-zero (NRZ)
phase-shift keying (PSK) pulse coding. An I/Q detection unit allows for a full (amplitude,
phase and polarization) characterization of the backscattered optical signal, thus achieving a
fully linear system in terms of ΦOTDR trace coding/decoding. The technique can be used
with different modulation formats, and operation using 4 Gbaud single-polarization dual PSK
and 4 Gbaud dual-polarization quadrature PSK is demonstrated. As a proof of concept,
distributed sensing of dynamic strain with a sampling of 125 kHz and a spatial resolution of
2.5 cm (set by the bit size) over 500 m is demonstrated for applied sinusoidal strain signals of
500 Hz. The limitations and possibilities for improvement of the technique are also discussed.European CommissionMinisterio de Economía y CompetitividadComunidad de Madri
Spectrally-efficient 17.6-Tb/s DWDM optical transmission system over 678 km with pre-filtering analysis
Artificial realism Form and content in Elizabethan fiction
SIGLEAvailable from British Library Document Supply Centre- DSC:D90602 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Throughput gains from adaptive transceivers in nonlinear elastic optical networks
In this paper, we link the throughput gains, due to transceiver adaptation, in a point-to-point transmission link to the expected gains in a mesh network. We calculate the maximum network throughput for a given topology as we vary the length scale. We show that the expected gain in the network throughput due to transceiver adaptation is equivalent to the gain in a point-to-point link with a length equal to the mean length of the optical paths across the minimum network cut. We also consider upper and lower bounds on the variation of the gain in the network throughput due to transceiver adaptation, where integer-constrained channel bandwidth assignment and quantized adaptations are considered. This bounds the variability of results that can be expected and indicates why some networks can give apparently optimistic or pessimistic results. We confirm the results of previous authors that show finer quantization steps in the adaptive control lead to an increase in the throughput since the mean loss of throughput per transceiver is reduced. Finally, we consider the likely network advantage of digital nonlinear mitigation and show that a significant tradeoff occurs between the increase in the signal-to-noise ratio for larger mitigation bandwidths and the loss of throughput when routing fewer large-bandwidth superchannels
Impact of amplifier noise figure on network throughput
The impact of the amplifier noise figure (NF) on the optical network throughput is quantified from an information viewpoint. For every dB of NF decrease, throughput gains between 4% and 7% are reported
On optimal modulation and FEC overhead for future optical networks
Transceivers employing square PM-QAM with up to two FEC overheads are optimized based on the SNR distribution. For NSFNET two FEC overheads with PM-16QAM give an 82% throughput increase compared with PM-QPSK with 7% overhead