WDM Optical Link Research Articles

Transmission of 112 Gb/s dual-carrier DQPSK signal over 10 Gb/s-based WDM optical links

The 112Gb/s dual-carrier differential quadrature phase shift keying (DC-DQPSK) optical transceiver, which does not need digital signal processing and coherent detection, is proposed for cost-effective 100G transport solution. In this paper, we describe upgrade schemes of 10Gb/s-based WDM optical links by adopting 112Gb/s DC-DQPSK transceiver, while the dispersion of the optical links is compensated 100% at each span. Method of introducing the DC-DQPSK signal into single grid of 100GHz spaced WDM link is demonstrated. Performance sufficient for error-free operation after forward error correction is achieved over 640km standard single mode fiber (SSMF) link. In another method, we experimentally investigate the transmission performance with co-propagating 10.7Gb/s on-off-keying (OOK) signals over 1000km of SSMF when the dual carriers occupy two channel grids separately. Excellent tolerance to the nonlinearities impacted by the OOK signals and low optical signal-to-noise ratio requirement are verified to demonstrate superior transmission performance in 10Gb/s-based WDM links.

동적 레인 제어방식을 적용한 에너지 절감형 광 이더넷 시스템의 성능분석

In this paper, we propose a dynamic lane control scheme with a traffic predictor module and a rate controller for reconciling with commercial optical PHY modules in energy efficient optical Ethernet systems. The commercial high speed optical Ethernet system capable of 40/100Gbps employs 4 or 10 multiple optical transceivers over WDM or multiple optical links. Each of the transceivers is always turned on even if the link is idle. To save energy, we propose the dynamic lane control scheme. It allows that several links may be entirely turned off in a low traffic load and frames are handled on the remaining active links. To preserve the byte order even if the number of active links may be changed, we propose a rate controller to be sat on the reconciliation sublayer. The main role of the controller is to insert null byte streams into the xGMII of inactive lanes. For the PHY module, the null input streams corresponding to inactive lanes will be disregarded on inactive PMDs. It is very handy to implement the rate controller module with MAC in FPGA without any modification of commercial PHYs. It is very crucial to determine the number of active links based on the fluctuated traffic load, we provide a simple traffic predictor based on both the current transmission buffer size and the past one with different weighting factors for adapting to the traffic load fluctuation. Using the OMNET++ simulation framework, we provide several performance results in terms of the energy consumption.

XPM-induced crosstalk with variety of fiber in SCM–WDM optical transmission link

In this paper, XPM-induced crosstalk has been evaluated in a SCM–WDM communication link at different modulation frequencies, transmission lengths and optical powers for variety of fiber. Results show that XPM-induced crosstalk dominates at high frequency. As the dispersion and effective area of fiber (Aeff) decrease, crosstalk increases with increase in modulation frequencies, transmission lengths and optical powers. The present work shows that out of five different types of fiber, Standard Single Mode Fiber (SMF) has minimum crosstalk (−78 to −38)dB, (−55 to −33)dB and (−46 to −34)dB at modulation frequencies, transmission lengths and optical powers. Dispersion compensation fiber (DCF) has maximum crosstalk (−60 to −12)dB, (−37 to −12)dB and (−27 to −12)dB at modulation frequencies, transmission lengths and optical powers.

Improved XPM-induced crosstalk with higher order dispersion in SCM–WDM optical transmission link

In this paper, the XPM-induced crosstalk has been evaluated with higher order dispersion in SCM–WDM optical transmission link at different modulation frequencies, transmission lengths and optical powers. It has been observed that there is exponent increase in XPM-induced crosstalk with the increase in modulation frequencies, transmission lengths and optical powers, respectively. The impact of 3OD, 4OD and 5OD is small as compared to 2OD but still contributes when the combined terms are considered. The combined effect of second, third, fourth and fifth-order dispersion parameters, the induced crosstalk introduced by XPM little increase.

XPM-induced crosstalk with combined effect of 2OD and 3OD in SCM–WDM optical transmission link

In this paper, the XPM-induced crosstalk has been evaluated with combined effect of second order Dispersion (2OD) and third order Dispersion (3OD) in SCM–WDM optical transmission link for varied dispersion parameters in different modulation frequencies and transmission lengths. It has been observed that there is significant effect of 2OD and 3OD on the XPM-induced crosstalk in a SCM–WDM transmission link. It has been observed that XPM-induced crosstalk lies between (−54 to −30) to (−42 to −18) dB and (−54 to −28) to (−38 to 16) dB in the presence of combined effect of 2OD and 3OD respectively for dispersion varied from 5ps/nm/km to 20ps/nm/km. Hence it observed that there is exponent increase in XPM-induced crosstalk with the increase in different modulation frequencies and transmission lengths and as dispersion increases, XPM-induced crosstalk also increases.

Ultralow Power 80 Gb/s Arrayed CMOS Silicon Photonic Transceivers for WDM Optical Links

Silicon photonic interconnects offer a promising solution to meeting the ever growing demand for more efficient I/O bandwidth density. We report an ultralow power 80 Gb/s arrayed silicon photonic transceiver for dense, large bandwidth inter/intrachip interconnects. Low parasitic microsolder-based hybrid bonding enables close integration of silicon photonic array devices optimized on a 130 nm silicon-on-insulator CMOS platform with CMOS very large scale integration circuits optimized on a 40 nm silicon CMOS platform to achieve unprecedented energy efficiency. The hybrid CMOS transceiver consists of eight 10 Gb/s channels with a total consumed power below 6 mW/channel. The eight-channel wavelength division multiplexing transmitter array using cascaded tunable ring modulators demonstrated better than 100 fJ/bit energy efficiency for 10 Gb/s operation excluding the laser power and tuning power, while the eight-channel receiver array using broadband Ge p-i-n waveguide detectors show sensitivity of better than -15 dBm for a bit error rate of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> at a data rate of 10 Gb/s with energy efficiency of better than 500 fJ/bit.

XPM-induced crosstalk with higher order dispersion in SCM–WDM optical transmission link

In this paper, the XPM-induced crosstalk has been evaluated with higher order dispersion in SCM–WDM optical transmission link at different modulation frequencies. It has been observed that there is exponent increase in XPM-induced crosstalk with the increase in modulation frequency from 0 to 3GHz. The impact of 3OD, 4OD and 5OD is small as compared to 2OD but still contributes when the combined terms are considered. The combined effect of second, third, fourth and fifth-order dispersion parameters is that the induced crosstalk introduced by XPM increases.

Simulative analysis of pre- and post-compensation using CRZ format in WDM optical transmission link

This paper reports the effects of pre- and post-compensation using CRZ modulation format in long-haul WDM optical transmission link using wavelengths in three bandwidths viz. 1537.4; 1550; 1562.6 nm at per channel bit rates of 10 Gbit/s. It has been investigated here that optimization of dispersion map results in improved management of nonlinear effects in long-haul light wave systems operating in the quasi-linear regime. In addition, pre- and post-dispersion compensation was applied at the transmitter and receiver depending on the signal wavelength, which resulted in improvement of performance metrics viz. Q 2 (dB), BER and OSNR over longer transmission distances. It is reported here that optimum values of Q 2 dB of 17.1 dB, BER of 8.4933e −015 and OSNR of 30.1 dB are obtained at 1550 nm at a transmission distance of 7360 km with pre- and post-compensation using CRZ modulation format.

A Nested Noncooperative OSNR Game in Distributed WDM Optical Links

This paper develops a Nash game formulation for optical signal-to-noise ratio (OSNR) in distributed optical links. The starting point is a recent network OSNR model developed for optically amplified links whereby channel powers are adjusted independently only at transmitter sites. A more general case is considered here where channel powers are also adjustable at intermediary dynamic sites, specific to optical networks. For this inherent distributed configuration a nested Nash game is formulated towards minimizing channel OSNR degradation along the link. Existence and uniqueness of the Nash equilibrium solution is shown and a recursive procedure for constructing it is given. Based on this, an iterative algorithm that is distributed with respect to both channels and -spans is proposed.

A Nested Noncooperative OSNR Game in Distributed WDM Optical Links

A Nested Noncooperative OSNR Game in Distributed WDM Optical Links

Characterization of a 4$\,\times\,$4 Gb/s Parallel Electronic Bus to WDM Optical Link Silicon Photonic Translator

A 4times4 Gb/s microring modulator cascade, which can directly convert data from a parallel electrical bus to a multiple-wavelength optical signal in a single silicon-on-insulator waveguide, is demonstrated and characterized. The integrity of the modulated optical signal is verified using Q-factor extrapolations. In addition, the frequency characteristics and crosstalk, in terms of total harmonic distortion, are quantified. A transparent translator from electronics to optics such as this is crucial for the development of large-scale high-bandwidth interconnects based on photonic integrated circuits

Suppression of Rayleigh backscattering in a bidirectional WDM optical link using clipped direct modulation

A novel technique is presented to reduce the Rayleigh-backscattering-induced noise in a bidirectional optical link where the same wavelength is used. The interferometric noise in bidirectional optical links can be reduced by control of the coherence time of the optical source. A clipping modulation of the laser diode provides effective noise spreading. Verification of the proposed technique has been performed through a transmission experiment.