Crosstalk Power Penalty Research Articles

Design and analysis of hybrid optical distribution network for worst-case scenario of E2-class symmetric coexistence 80 Gbps TWDM NG-PON2 architecture for FTTX access networks

In this paper, we investigated the cost-effective design and validation of E2-class coexistence 80 Gbps symmetric 8 × 8 Time and Wavelength Division Multiplexing (TWDM) NG-PON2 optical access network considering worst-case scenario for the deployment of Fiber-to-the-X (FTTX) access network using hybrid optical distribution network (ODN). Full-service access network (FASN) unanimously agreed and ITU-T G.989.2 described recommendations for TWDM PON NG-PON2 technology to cater to the need of ever-increasing demand for higher bandwidth and data speed beyond 10 Gbps per user through access networks. Wavelength select (WS) and wavelength-routed (WR) ODN for downstream (D/S) and upstream (U/S) channels symmetric coexistence functionality supporting 80 Gbps accommodating GPON and XGS-PON legacy channels i.e.4-TWDM and 4 point-to-point (PtP) WDM channels operating at 1.25/2.5/10 Gbps respectively in D/S and U/S direction with error free higher splitter configuration of 2304 at 20 km, 640 at 40 km, 576 at 60 km. Precise calculations are done to ensure 11 dBm and 9 dBm ODN launch power (PTODN) to implement worst-case scenario for symmetric E2-class TWDM NG-PON2 network. Calculated inter-channel cross-talk (Cc) is -33.57 dB/-34.74 dB and corresponding cross-talk power penalty (Pc) is 0 dB for D/s and U/S channels respectively. Simulation results demonstrated and verified with the recommendations made in ITU-T G.989.2 confirmed that the proposed network configuration supports extended to reach upto 60 km in D/S and 80 km in U/S direction delivering incremental receiver sensitivity (Rxs) as -34.40/-34.40/42.21 dBm and -34.11/-37.25/-33.37 dBm, ODN path loss 29.40 dB.

Crosstalk Penalty in Microring-Based Silicon Photonic Interconnect Systems

We examine inter-channel and intra-channel crosstalk power penalties between non-return-to-zero on-off keying (NRZ-OOK) wavelength-division-multiplexing (WDM) channels for microring-based silicon photonic interconnects. We first propose a new model that relates the crosstalk power penalty to the interfering signals power, the extinction ratio of the non-return-to-zero, OOK modulated “victim” channel, and finally the bit-error-ratio that the power penalty is referenced to. As for inter-channel crosstalk, the proposed model agrees well with our recent experimental measurements. We leverage this model to quantify crosstalk induced power penalties in a microring based WDM receiver. We also propose an optimization procedure to equilibrate the power penalty across channels. We then compare our model with intra-channel crosstalk measurements, where two NRZ channels are at the same wavelength and are simultaneously routed to different paths by two cascaded ring resonators. We remark that intra-channel crosstalk is very sensitive to the data rate of NRZ channels. As data rate increases, the observed disturbances exceed what models predict. Based on these observations, we propose an empirical modification of the original model for estimating intra-channel crosstalk power penalties in high ( $>$ 20 Gb/s) data rate situations.

Crosstalk in SOI Microring Resonator-Based Filters

We experimentally investigate the interchannel and intrachannel crosstalk of first- and second-order microring resonator (MRR) filters fabricated on a silicon-on-insulator platform. We find that there is an MRR radius that maximizes the wavelength division multiplexing channel count given a waveguide geometry, a maximum tolerable insertion loss, and a minimum permissible adjacent channel isolation. The measured power penalties due to interchannel crosstalk of two-channel demultiplexers based on first-order and series-coupled MRR filters are presented as functions of channel spacing and adjacent channel isolation. Next, we compare the intrachannel crosstalk of first-order, cascaded, and series-coupled MRR add-drop filters. Our results show that first-order MRR devices are unsuitable for simultaneous add-drop operation at high data rates and small channel spacings. Intrachannel crosstalk of cascaded and series-coupled designs are measured as functions of the data rate and the level of detuning between the MRRs. Low intrachannel crosstalk power penalties are demonstrated for cascaded and series-coupled MRR filters for data rates up to 20 Gb/s. Based on the measured results, we present requirements for the input-to-through response of add-drop filters that will ensure low intrachannel crosstalk.

Analytical Analysis of In-Band Crosstalk, Out-of-Band Crosstalk and GVD-Based Power Penalties in DWDM and TDM/DWDM-PONS

In addition to the ever-increasing demand for broader bandwidth per user, which results from the continuous development of new bandwidth-hungry services and applications, the consequent upgrade from the currently deployed Time-Division Multiplexing Passive Optical Networks (TDM-PONs) to Next-Generation Optical Access Networks (NG-OANs) has become inevitable. Different architectures for creating a NG-OAN have been proposed in the literature. Among those architectures, the DWDM and TDM/DWDM-Based OANs are very promising candidates. They were mainly proposed to exploit the large wavelength counts available in the fibre (its virtual unlimited bandwidth) to achieve a significant increase in the system capacity. Moreover, they allow coexistence in an open access environment among different network operators. In this study, we first analyze the impact of in-band crosstalk, out-of-band crosstalk to evaluate the performance of the Arrayed Waveguide Grating (AWG). The reason to focus on the AWG is due to this optical device is used almost in all DWDM and TDM/WDM-PONs. We then turn our attention to analyze the impact of group velocity dispersion GVD to estimate the maximum allowable bit rate for optical transmission without the need for using a Dispersion Management Technique (DMT) and/or a Forward Error Correction Technique (FECT). The analysis was performed using Matlab software (The Math works, Inc., Natick, MA, USA) and confirms that the in-band crosstalk has a stronger effect than the out-of-band crosstalk because its noise floor is reached at a lower crosstalk noise and with fewer crosstalk components. The in-band crosstalk noise should be kept below -37 dB and -34 dB to maintain a power penalty of less than 1 dB if 15 and 7 in-band crosstalk components are considered, respectively. The out-of-band crosstalk noise should be kept below -20.3 dB and -17.18 dB to maintain a power penalty of less than 1 dB if 240 and 56 out-of-band crosstalk components are considered, respectively. It was observed that the GVD noise floor is reached at a shorter fiber length as the bit rate increases and it was confirmed that a significant improvement in which the GVD noise floor is reached at longer fiber can be achieved if an externally modulated, small spectral-width source is used when a bit rate of 622 Mbps, 1 Gps, or 2.5 Gbps is used. However, a dispersion management technique becomes necessary if the bit rate increases to 10 Gbps or more.

Power Penalty Assessment of OXADM Device Model - Analytical Analysis

This OXADM are located in the nodes, which have more than two switching directions in ring networks. The function of OXADM is to flexibility switch the wavelengths among the different input and output ports. Because of the OXADM's imperfect performance, the insertion loss and crosstalk are induced in the system. Analytical modeling method is using to analyze the OXADM structure in crosstalk or power leakage that lead to the power penalty. To overcome this problem, power penalty is needed to be supplied. The insertion of this power penalty depends on few parameters. The parameters that we going to investigate here will be in term of number of operating wavelengths and number of input/output ports as well as the Q factor. The variation of this parameters will affects the amount of the desired power penalty. Simulation results in higher crosstalk or higher power penalty needed as the number of OXADM increases. As the sum of the wavelength and the number of input/output for each OXADM increases, the power penalty will increased as well. Investigation on the maximum Q factors is 6 to get the minimum power penalty at the lowest BER for most of the combination of the sum of the wavelength and the number of input/output for each OXADM.

Interferometric Crosstalk Reduction in an RSOA-Based WDM Passive Optical Network

Reflection and Rayleigh backscattering-induced interferometric crosstalk in a link employing a reflective semiconductor optical amplifier (RSOA) may cause significant power penalty and, thus, limit the performance of the system. In this paper, we investigate interferometric crosstalk suppression in a centralized light generation wavelength division multiplexing-passive optical network (WDM-PON) by single-tone phase modulation either by utilizing the nonlinear behavior of the RSOA at the optical network unit (ONU) or by applying an external phase modulator at the source side. 6- and 7-dB reduction in power penalty for reflection-induced crosstalk is achieved, respectively. For Rayleigh backscattering-induced crosstalk power penalty is improved with 3 and 4.5 dB, respectively. The results show that an RSOA is very sensitive to reflections and backscattering and the tolerance to these impairments can be significantly improved by appropriate phase modulation. A comparison with advantages and disadvantages of both methods together with final recommendation is also given in the paper.

A 3.125Gbit/s Parallel Optical Receiver in 0.13-{mu} CMOS with Direct Crosstalk Power Penalty Measurement Capability

We introduce a new method to measure the crosstalk power penalty in an arrayed environment by using an on-chip pseudorandom-bit-sequence generator to drive the aggressors. The proposed method is implemented in a three-channel 3.125-Gbit/s/ ch parallel receiver. Experimental results are presented including measurements of bit-error rate and crosstalk power penalty for 2.5and 3.125-Gbit/s operations. The measured crosstalk power penalty is less than 1 dB at both data rates. The test chip was designed in a standard 0.13-mum CMOS process

All-optical multi-wavelength conversion using absorption modulation of an injection-locked FP-LD

An all-optical multi-wavelength converter using absorption modulation of an injection-locked Fabry-Perot laser diode (FP-LD) is demonstrated at 2.5Gb/s. The multi-wavelength converter can simultaneously provide 1 to 4 channel outputs and support both inverted and non-inverted conversion. By optimizing the wavelength of pump signal and polarization states of pump, probes, and the FP-LD, all converted outputs show high extinction ratio and negligible crosstalk power penalty. The results guarantee to increase the number of output channels. The proposed scheme can be applied to multicasting functions as well as 1xN wavelength conversion in an all-optical wavelength division multiplexed network.

A 3.125-Gbit/s Parallel Optical Receiver in 0.13-<formula formulatype="inline"><tex>$\mu{\hbox {m}}$</tex></formula> CMOS With Direct Crosstalk Power Penalty Measurement Capability

We introduce a new method to measure the crosstalk power penalty in an arrayed environment by using an on-chip pseudorandom-bit-sequence generator to drive the aggressors. The proposed method is implemented in a three-channel 3.125-Gbit/s/ ch parallel receiver. Experimental results are presented including measurements of bit-error rate and crosstalk power penalty for 2.5and 3.125-Gbit/s operations. The measured crosstalk power penalty is less than 1 dB at both data rates. The test chip was designed in a standard 0.13-mum CMOS process

Study of crosstalk property in an optical packet switching node

The effect of queuing delay of output buffer on the crosstalk property in optical packet switching nodes is investigated. The relationship between crosstalk and buffer length is obtained. From the calculation and simulation results, it is concluded that the crosstalk power penalty predominantly depends on the buffer length, the longer the buffer, the greater the penalty, as well as the random range of the penalty. While comparing with the effect of queuing delay, the effect of random routing path delay takes very little proportion in the total power penalty.

Highly stable optical add/drop multiplexer using polarization beam splitters and fiber Bragg gratings

We demonstrate a novel wavelength-division add/drop multiplexer employing fiber Bragg gratings and polarization beam splitters. The multiplexer is easy to fabricate without any special technique such as UV trimming, and yet shows very stable performance with less than 0.3-dB crosstalk power penalty in a 0.8-nm-spaced, 2.5-Gb/s-per-channel wavelength-division multiplexing (WDM) transmission system.

BER impairment due to laser linewidth in OFDM-OOK systems using double-cavity Fabry-Perot demultiplexers

We report on the impact of finite laser linewidth on the bit error rate (BER) performance in directly detected optical frequency-division multiple-access (OFDMA) employing double-cavity Fabry-Perot (FP) filters. Three different double-cavity FP demultiplexers have been considered in this study. Also the laser linewidth impairment on the crosstalk probability mass functions, the crosstalk power penalties and the OFDMA network capacity are calculated. The results demonstrate that, even though these demultiplexing schemes are much superior than single-cavity FP filters for highly coherent sources (laser linewidth lower than a few megahertz), when laser linewidth increases this feature appears to be much less significant due to the severe impairment of the laser linewidth on the BER performance, specially for structures with higher optical filter finesse.

Analysis of linear crosstalk in photonic crossbar switches based on on/off gates

This paper presents expressions for the linear crosstalk and the resulting error rate degradation in a photonic switch based on on/off gates, considering cyclostationary interference among digital signals. The periodically time-varying interference accounts for the dependencies of error probability both on the spectrum of transmitted signals and on random bit-skews between channels. This paper quantitatively verifies the intuitions that bit-aligned channels increase the crosstalk power penalty, and that a sharp modulating pulse improves error probability. These dependencies on spectrum and bit-skews become noticeable at high crosstalk levels caused by either a low contrast ratio or a large switch size.

Performance assessment of two-channel dispersion-supported transmission systems using single- and double-cavity Fabry-Perot filters as demultiplexers

This letter presents a theoretical performance assessment assuming that single- and double-cavity Fabry-Perot filters are used as demultiplexers in two-channel dispersion supported transmission systems operated at 10 Gb/s. A suitable simulation methodology has been used that combines signal simulation with noise analysis in optically amplified multichannel direct detection systems. The results obtained show an improved system performance if a double-cavity Fabry-Perot filter is used as a demultiplexer, resulting in a WDM transmission with a crosstalk power penalty within 1 dB in the region of low dispersion penalty of the DST method, for a channel spacing of 1 nm. The robustness against dependencies on data patterns is verified.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Crosstalk penalties in a bidirectional fiber-optic WDM system

Crosstalk power penalties were calculated for a bidirectional fiber-optic wavelength division multiplexed (WDM) system (622 Mb/s at 1300 nm in one direction and 155 Mb/s at 1550 nm in the other) using the system simulation program Simulation of Fiber-Optic Communication Systems (SIFOCS). Nonreturn-to-zero (NRZ) and return-to-zero (RZ) modulation formats were investigated with the result that, in most cases, the power penalty was shown to depend only weakly on individual system properties and is close to the values found in the literature, but there are exceptions where it may be greater than usual (e.g. at 622 Mb/s RZ). These can be detected and investigated with the methods reported. The crosstalk power penalty becomes excessive only for signal-to-crosstalk power ratios well below 10 dB and is negligible for values greater than 15 dB. The calculation methods used can be easily adapted to other systems, e.g. to systems with more closely spaced wavelengths. >

Crosstalk analysis and filter optimization of single- and double-cavity Fabry-Perot filters

Since Fabry-Perot (FP) filters are major candidates for use as demultiplexers in wavelength division multiple access (WDMA) networks, the authors have analyzed, in an exact and unified manner, the crosstalk degradation for several different variations of the basic FP filter, compared their performances, and optimized their design parameters. A description is given of the system model (a wavelength division multiple access system consisting of M connected transmitters and receivers with each transmitter consisting of an on-off modulated fixed-frequency laser, with the 'off' power level equal to zero) and the parameters used throughout, along with a brief discussion of relevant Fabry-Perot equations and terms and the four different filter structures analyzed. The crosstalk is examined for the cases of a single-cavity FP filter, a double-pass FP filter, a two-stage double-cavity FP filter, and a vernier double-cavity FP filter. The criteria for the performance comparison were the worst-case crosstalk, BER, and crosstalk power penalty.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>