Burst-Mode FPGA Implementation and Error Location Analysis of Forward Error Correction for Passive Optical Networks

The performance of forward error correction (FEC) based on Reed-Solomon coding is analyzed experimentally for a burst-mode upstream channel within a passive optical network (PON) testbed. During this analysis, the upstream FEC performance is impaired by inducing correlated and localized errors within the burst through the injection of optical transients. These transients emulate the optical signal variation associated with the add-and-drop events of wavelength channels within a long-reach optical link based on a chain of erbium doped fiber amplifiers (EDFAs). The robustness of the FEC has been analyzed by measuring the post-FEC bit error rate (BER) as a function of the amplitude of the emulated transients and their delay with respect to the transmitted bursts. A margin of approximately 4dB is demonstrated for the transient amplitude before the FEC degradation. Furthermore, while the post-FEC BER is strongly degraded by the emulated transients, the pre-FEC BER stays below the FEC threshold, demonstrating the importance of measuring the post-FEC BER in order to correctly characterize the FEC performance in PON upstream channels affected by optical transients.

This paper presents an experimental flexible Field Programmable Gate Array (FPGA) based platform for testing and verifying digital controlled dc-dc converters. The platform supports different types of control strategies, dc-dc converter topologies and switching frequencies. The controller platform has a synchronized load change mechanism and build-in acquisition memory, which makes it possible to, easily compare and verify different control strategies. Besides the main controller tasks, the logic also contains a digital to analog module, that can be used for eq. outputting a controller parameter, for easy inspection on an oscilloscope in real time. The platform is implemented with low coupling between logic modules with a modular design, which allows changes, update of features and/or adding functionality, if needed. The platform has an operating system independent controller host interface supporting configuration and reading of setup parameters, controller status and the acquisition memory in a simple way. The FPGA based platform, provides an easy way within education or research to use different digital control strategies and different converter topologies controlled by an FPGA without deep knowledge about Hardware Description Language (HDL).

Cell rate moderation of VBR video under an FEC environment in ATM networks

In this paper we evaluate the performance of forward error correction (FEC) techniques in the presence of four wave mixing (FWM) and dispersion induced inter-symbol interference (ISI). A comparison with the detuning technique [1] is also presented, for the case of FWM penalty mitigation. FEC has been widely used in long haul submarine optical transmission systems, both repeated [2] and unrepeated [3] and its performance in the presence of polarization mode dispersion (PMD) has also been investigated [4,5]. The influence of non-linearities on optical systems that use FEC has recently been reported [6].

In this paper, we present a detailed and marketing - free study of all components of the upstream and downstream channel transmission overhead for Ethernet Passive Optical Networks (EPONs), excluding optional Forward Error Correction (FEC). First, the general Ethernet framing overhead is evaluated, followed by in depth analysis of each overhead component related to operation of the EPON MPCP protocol. Their overall impact on the performance of the system (especially in the upstream channel) is quantified for both best and worst case scenarios using typical system parameters, characteristic of standard EPON deployments. Based on a set of standard-based and typical EPON parameters, an estimated throughput of approximately 820 to 900 Mbit/s is available in the upstream direction, while in the downstream the effective throughput ranges from around 915 to 935 Mbit/s, producing the channel efficiency figures of 82 to 90% and 91.5 to 93.5% , respectively, relative to the effective data rate of 1 Gbit/s.

Broadband Passive Optical Access Networks

An FEC scheme combined with weighted scheduling to reduce multicast packet loss in IPTV over PON

Passive Optical Networks (PON) have advantages such as stable performance, convenient installation, high bandwidth, and resource saving, making them a mainstream network access technology with broad application prospects. The development of such as 8K video, digital twins, VR and other technologies causes explosive growth of network traffic and drives the next generation of PON to evolve towards higher rates, which results in the use of forward error correction (FEC) coding with higher coding gain to improve the power budget of PON. Quasi-cyclic low density parity check (QC-LDPC) codes are widely utilized in PON systems due to high coding gain and parallel encoding and decoding capabilities. However, the application of turbo-decode message passing (TDMP) decoding method is inevitably equated with high hardware complexity of the decoder caused by storing and processing massive information, which is one of the obstacles to PON evolution. Reducing the quantization word length is effective to reduce hardware complexity, but it also leads to saturation of decoding information, causing errors and affecting decoding performance. This work proposes an nonlinear mapping method which utilizes adaptive compression of decoding information through node saturation state monitoring during the decoding process, in order to ensure that the probability density of node information has a reasonable distribution. The simulation results indicate that the method can effectively mitigate the decline in decoding performance under low-word-length conditions.

Fiber-to-the-home (FTTH) or close to it (FTTx) networks are poised to become the next major success story for optical fiber communications. Future FTTx access networks unleash the economic potential and societal benefit by opening up the first/last mile bandwidth bottleneck between bandwidth-hungry end-users and high-speed backbone networks. Owing to their longevity, low attenuation, and huge bandwidth, passive optical networks (PONs) are widely deployed to realize cost-effective FTTx access networks. Fiber has been envisioned for delivering broadband services for over 30 years. However, many roadblocks related to component and installation costs have slowed down the progress toward FTTx since it was first proposed. Currently, FTTH is being installed in many countries, but it still represents only a fraction of all deployed broadband lines (Shumate [2008]). The two major state-of-the-art PON standards IEEE 802.3ah Ethernet PON (EPON) and ITU-T G.984 Gigabit PON (GPON) consist both of a single upstream wavelength channel and a separate single downstream wavelength channel, whereby both channels are operated using time division multiplexing (TDM). EPON and GPON are expected to coexist for the foreseeable future as they evolve into next-generation PONs (NG-PONs) (Effenberger et al . [2007], Kazovsky et al . [2007]). NG-PONs can be categorized into high-speed TDM PON, wavelength division multiplexing (WDM) PON, and long-reach PON (LR-PON) (Lin [2008], Effenberger et al . [2009a]).

Power budget of direct-detection ultra-dense WDM-Nyquist-SCM PON with low-complexity SSBI mitigation

This work presents a new approach on dynamic bandwidth allocation (DBA) for Ethernet Passive Optical Networks (EPONs). A brief introduction to the DBA area and major term definitions are given. The related research and standardization efforts are presented. Justification that EPONs can be used on the aggregation network is provided, based on their evolution and related research proposals. Focus is given to the Long Reach-Passive Optical Networks (LR-PONs) and their limitations which show the need for a non-polling, midterm DBA scheme for next-generation EPONs. The challenges arising, because of this new approach, are discussed along with possible solutions. Finally, this work proposes the EMDBA algorithm which is able to overcome the discussed issues. The correct operation of this algorithm is confirmed by a set of simulations using OMNet++ framework, and the outcome results show that EMDBA performance is satisfactory in terms of delay and service differentiation.

Mode-division multiplexing passive optical network (MDM-PON) is a promising scheme for next-generation access networks to further increase the transmission capacity and number of end-customers. In this paper, we propose and experimentally demonstrate the implementation of MDM-PON architecture with the carrier-less amplitude/phase (CAP) modulation signals and two effectively separated spatial modes multiplexing transmission in an elliptical-core few-mode fiber (EC-FMF). The trench-assisted EC-FMF features favorable anti-bending performance with negligible power variations and stable mode intensity profiles under extreme bending conditions. Two spatial modes carrying CAP-16 signals for four users with net data rate of 5 Gb/s per user in the downstream transmission over 1.1-km EC-FMF is demonstrated. The measured mode crosstalk including mode (de)multiplexing and 1.1-km EC-FMF transmission is less than -18 dB and multiple input multiple output (MIMO) technique is not used in the experiment for simplicity. The measured optical signal-to-noise ratio (OSNR) penalties for the downstream transmission without or with crosstalk at a bit-error rate (BER) of 3.8x10-3 (7% forward error correction (FEC) threshold) are less than 1.8 dB and 3.1 dB, respectively. Larger transmission capacity and more users are expected when further employing higher dimension CAP signals and EC-FMF supporting more separable spatial modes.

We propose a novel receiver configuration using an extreme narrow band-optical band pass filter (ENB-OBPF) to reduce the multiple access interference (MAI) and beat noises in an optical code division multiplexing (OCDM) transmission. We numerically and experimentally demonstrate an enhancement of the code detectability, that allows us to increase the number of users in a passive optical network (PON) from 4 to 8 without any forward error correction (FEC).

Forward error correction (FEC) technique has been widely used in wireless communication and mass storage applications. In recent years, FEC has also become very important to optical communication because of its powerful error correcting ability. FEC codes provide performance gain by trading off coding gain with coding redundancy and decoding complexity. For transmission bit rate of 10 Gb/s or higher, coding redundancy of less than 25% is desired. Therefore, FEC schemes with moderate coding redundancy and tolerable decoding complexity are desirable and very important for high-speed long-haul optical systems. In this thesis, two FEC augmentation schemes, namely wavelength interleaving and errors-and-erasures decoding (E&ED), are proposed to improve the FEC performance of optical channels subjected to polarization mode dispersion (PMD) and chromatic dispersion (CD). Wavelength interleaving provides frequency diversity, hence reducing the effective error burst length and improving FEC performance without requiring more coding redundancy. In E&ED scheme, an erasure zone is used to collect highly unreliable received symbols called erasure symbols.

Third generation fiber-to-the-x (FTTx) will introduce wavelength division multiplexing (WDM) technology to increase data rates up to 40 Gbit/s, as well as coexist with current communication systems. WDM passive optical network (WDM-PON) based fiber-to-the-home (FTTH) system architecture together with the Next-generation passive optical network (NG-PON) can provide solution related to nowadays problems with transmission capacity. It is expected that NG-PON systems will become more cost-efficient at high per user data rates, providing different transmission speeds for end users, based on pay-as-you-grow approach. In this paper, our introduced system model is used to obtain WDM-PON system effectiveness for different data rates of up to 32 Gbit/s per downstream transmission channel. We created combined simulative-experimental WDM-PON transmission system model in environment of RSoft OptSim simulation software to compare the performance of non-return-to-zero (NRZ) on-off-keying (OOK) modulated PON transmission system versus transmission bitrate and distance. Results showed that proposed transmission system is capable to provide data transmission of up to 32 Gbit/s per channel with BER $ , if additional forward error correction (FEC) is used. Additionally, to increase the reach of investigated system, fiber Bragg grating-based dispersion compensation module (FBG-DCM) is implemented, therefore enabling full pre-compensation of chromatic dispersion.