Q-factor estimation and impact of spontaneous-spontaneous beat noise on the performance of optically preamplified systems with arbitrary optical filtering

Rebola, Joao L.; Cartaxo, Adolfo V. T.

doi:10.1109/jlt.2003.808619

Cited by 23 publications

(25 citation statements)

References 21 publications

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“…As with digital SHD, if the LO laser is sufficiently well tuned, then digital domain filtering may be used to improve the transmission characteristics. In [24], a 0.5-dB improvement in the Q-factor was observed and a tolerance of up to 6 GHz to LO/signal detuning with the path length tolerance dependent on the bandwidth of the electrical filter. This technique was used for a long distance transmission of 10 × 128 Gb/s 16 QAM signals with 25 GHz spacing [56] over a distance of 1.815 km using 100 kHz linewidth lasers with phase noise cancellation, allowing a 1,650 km transmission for a 1-MHz linewidth DFB laser, an increase of 165 km from a SCR receiver, with frequency offset correction only.…”

Section: Transmissionmentioning

confidence: 95%

“…25 should appear after ref. 24 Equations (8) and (10) have been experimentally verified in [21,22], for PDM-SHD and SDM-SHD systems, respectively. However, it can be shown that the validity of this model is preserved for more general systems.…”

Section: Penalty Compared To Intradyne Detectionmentioning

confidence: 97%

“…The term, p, takes the values of one or two for single-polarization or polarization-multiplexed signals, respectively. Finally, σ 2 ns-np may be approximated using the rectangular filter approach [24] from directly-detected systems as:…”

Section: Penalty Compared To Intradyne Detectionmentioning

confidence: 99%

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Self-Homodyne Detection in Optical Communication Systems

et al. 2014

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Abstract:We review work on self-homodyne detection (SHD) for optical communication systems. SHD uses a transmitted pilot-tone (PT), originating from the transmitter laser, to exploit phase noise cancellation at a coherent receiver and to enable transmitter linewidth tolerance and potential energy savings. We give an overview of SHD performance, outlining the key contributors to the optical signal-to-noise ratio penalty compared to equivalent intradyne systems, and summarize the advantages, differences and similarities between schemes using polarization-division multiplexed PTs (PDM-SHD) and those using space-division multiplexed PTs (SDM-SHD). For PDM-SHD, we review the extensive work on the transmission of advanced modulation formats and techniques to minimize the trade-off with spectral efficiency, as well as recent work on digital SHD, where the SHD receiver is combined with an polarization-diversity ID front-end receiver to provide both polarization and modulation format alignment. We then focus on SDM-SHD systems, describing experimental results using multi-core fibers (MCFs) with up to 19 cores, including high capacity transmission with broad-linewidth lasers and experiments incorporating SDM-SHD in networking. Additionally, we discuss the requirement for polarization tracking of the PTs at the receiver and path length alignment and review some OPEN ACCESSPhotonics 2014, 1 111 variants of SHD before outlining the future challenges of self-homodyne optical transmission and gaps in current knowledge.

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Section: Transmissionmentioning

confidence: 95%

Section: Penalty Compared To Intradyne Detectionmentioning

confidence: 97%

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Self-Homodyne Detection in Optical Communication Systems

et al. 2014

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“…First, in a system that is optically amplified (as is the case with the CDS), amplified spontaneous emission (ASE) can beat with the LO and SBS signals and with itself. The noise variances are [44][45][46] …”

Section: Coherent Detection Schemementioning

confidence: 99%

Chirped fiber Brillouin frequency-domain distributed sensing

2014

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A frequency-domain distributed temperature/strain sensor based on a longitudinally graded optical fiber (LGF) is proposed and evaluated. In an LGF, the Brillouin scattering frequency, ν B , changes (i.e., is chirped) lengthwise monotonically and thus every position along the fiber has a unique ν B . Any change locally (at some position) in the fiber environment will result in a measurable change in the shape of the Brillouin gain spectrum (BGS) near the frequency component mapped to that position. This is demonstrated via measurements and modeling for an LGF with local heating. The LGF is one with ∼100 MHz Brillouin frequency gradient over 16.7 m, with 1.1 and 1.7 m segments heated up to 40 K above ambient. A measurement of the BGS can enable the determination of a thermal (or strain) distribution along a sensor fiber, thus rendering the system one that is in the frequency domain. A sensitivity analysis is also presented for both coherent and pump-probe BGS measurement schemes. The modeling results suggest that the frequency-domain systems based on fibers with a chirped Brillouin frequency are highly suited as inexpensive event sensors (alarms) and have the potential to reach submeter position determination with sub-1-K temperature accuracies at >1 kHz sampling rates. Limitations to the technique are discussed. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. IntroductionThe Brillouin scattering frequency, ν B , is related to the optical wavelength, λ o , and the acoustic velocity, V, by ν B ¼ 2Vn mode ∕λ o . It is well known that both the acoustic velocity and the refractive index of a glass usually are functions of its thermomechanical environment; i.e., temperature and any applied stress or strain to the material. The word "usually" is used as a qualifier because it is possible to realize multicomponent materials of which physical properties, such as the refractive index, are immune to temperature or strain/stress. 1-4 However, in conventional pure silica or GeO 2 -doped silica core optical fibers, the Brillouin scattering frequency is dependent on both the temperature and strain, with the usual dependence being an increasing frequency with increasing temperature or strain. 5 Since the temperature and strain dependencies of the Brillouin frequency (typically ∼1.2 MHz∕K 6 and 500 MHz∕%, 7 respectively, near 1550 nm for conventional fiber 5 ) are not insignificant, it is natural that this phenomenon has been adapted for use in distributed sensor technologies, [8][9][10][11] with very impressive results. High-sensitivity and resolution measurement schemes and configurations have been demonstrated, 12-20 and a commercial market exists for such distributed sensing systems. Resolution is defined in this context to be the ability to resolve two events that are in close proximity to each other, or alternatively, to resolve a certain temperatu...

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“…Therefore the Q-factor technique requires only measurements of the first two statistical moments of the marks and spaces levels. In many cases, the Q-factor method gives reasonable estimation of the real BER (Bergano et al 1993;Rebola and Cartaxo 2003), but it does so 'accidentally', in the sense that the optimum decision threshold predicted by this method is far away from the true optimum (Marcuse 1990). It has been shown that in most cases Q-factor gives conservative BER estimations (Marcuse 1990;Ribeiro et al 1995).…”

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confidence: 99%

Optical signal quality metric based on statistical moments and Laguerre expansion

2008

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A new and straightforward optical signal quality metric, which is based on the approximation of the analytical probability density function by its Laguerre expansion, is proposed. This expansion uses statistical moments to approximate the true statistics, but, unlike the well-known Gaussian approximation, higher order moments can be used as well. The quality of the proposed metric is discussed and the metric is compared with the Gaussian approximation. It is shown that the new metric provides not only a good estimation of the bit error rate in the range of practical interest but, contrary to the Gaussian approximation, correctly estimates optimum decision threshold and accurately pictures the shape of the noise distribution.

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Q-factor estimation and impact of spontaneous-spontaneous beat noise on the performance of optically preamplified systems with arbitrary optical filtering

Cited by 23 publications

References 21 publications

Self-Homodyne Detection in Optical Communication Systems

Self-Homodyne Detection in Optical Communication Systems

Chirped fiber Brillouin frequency-domain distributed sensing

Optical signal quality metric based on statistical moments and Laguerre expansion

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