Time division multiplexing passive optical networks (TDM-PONs) are the most widely deployed optical system solutions in current broadband access networks worldwide. The energy and cost efficiency of ...both their implementation and operation has reached levels that also make them an attractive option for other cost sensitive communication networks. We discuss how essential features of current TDM-PON specifications can be leveraged to also use them for low latency and high capacity professional services in public and private networks. Also, possible PON architecture evolutions towards added intra-PON communication are outlined that are motivated by the latency requirements of some practical use cases.
Abstract
The immense growth of data traffic that traverses modern networks, calls for immediate solutions to tackle the challenges that arise in terms of speed, capacity, cost and energy efficiency. ...This manuscript outlines the key technological aspects of the PICaboo project, that aims to develop novel building blocks and photonic integrated circuits for the next generation of optical metro and access networks enhanced with optical signal processing functionalities exploiting the generic foundry model approach.
Next-generation passive optical networks (PONs) with upstream rates of 50 Gbit/s and beyond will require a new class of burst-mode transimpedance amplifiers (BMTIAs) that are linear to enable ...(digital) equalization of channel impairments. Such linear BMTIAs also enable higher-order modulation formats like 4-level pulse amplitude modulation (PAM-4). In this paper, we demonstrate operation of a novel linear BMTIA integrated together with a commercial off-the-shelf 25G-class avalanche photodiode (APD), achieving 50 Gbit/s non-return-to-zero (NRZ) operation with a sensitivity of -23.7 dBm optical modulation amplitude (OMA) and dynamic range exceeding 21.7 dB and 100 Gbit/s PAM-4 operation with a sensitivity of -15.8 dBm OMA and dynamic range exceeding 15.4 dB, both at a bit error ratio (BER) of <inline-formula><tex-math notation="LaTeX">10^{-2}</tex-math></inline-formula>. In addition, fast burst-mode gain-control and balancing circuits limit loud-soft sensitivity penalties in the case of AC-coupled circuits to less than 1.3 dB. The chip was designed in a 0.13 <inline-formula><tex-math notation="LaTeX">\mu</tex-math></inline-formula>m SiGe:C BiCMOS technology, has an area of 1.2×1.7 mm<inline-formula><tex-math notation="LaTeX">^{2}</tex-math></inline-formula> and consumes between 260 mW and 310 mW. This receiver paves the way to a next-generation class of BMTIAs, supporting the ITU-T G.9804.3 Amd 1 standard.
Wavelength conversion using cross-gain modulation (XGM) in quantum-dot (QD) semiconductor optical amplifiers (SOAs) is investigated. Small-signal measurements reveal that the XGM bandwidth as well as ...the conversion efficiency strongly depends on the bias current. Thus, it is possible to tune the XGM by increasing the current from a low efficiency with a 10-GHz bandwidth to a very efficient one with bandwidths well exceeding 40 GHz. Two different saturation mechanisms are responsible for this pronounced influence of the bias current: 1) total carrier depletion that leads to a slow broadband cross-gain saturation and 2) spectral hole burning that causes spectrally narrow-band high-speed XGM. With increasing current, the saturation by depleting the carrier reservoir, which feeds the QDs, is minimized, and therefore, spectral hole burning becomes more dominant. Large-signal wavelength conversion experiments using 50 ps pulses indicate that efficient high-speed XGM is feasible for pump and probe signal detuning up to 10 nm. With increasing detuning, larger pulse broadening and a decreasing efficiency are observed, consistent with the small-signal results. The results on the QD SOAs are compared to conventional quantum-well devices.
An ML-supported diagnostics concept is introduced and demonstrated to detect and classify events on OTDR traces for application on a PON optical distribution network. We can also associate events ...with ODN branches by using deployment data of the PON. We analyze an ensemble classifier and neural networks, the usage of synthetic OTDR-like traces, and measured data for training. In our proof-of-concept, we show a precision of 98% and recall of 95% using an ensemble classifier on measured OTDR traces and a successful mapping to ODN branches or groups of branches. For emulated data, we achieve an average precision of 70% and an average recall of 91%.
This JOCN Special Issue, which spans the September and October 2020 issues, investigates the future of passive optical networks (PONs) in light of new enabling technologies that are currently under ...consideration. The papers present a broad overview of topics of current interest, across both the physical and network layers. They investigate how new technologies (e.g., higher-speed direct detection transceivers, coherent systems, advanced digital signal processing, and new optoelectronic components) and new network-layer approaches may drive the medium- to long-term evolution of PONs.
Passive optical networks (PONs) facilitate small-cell deployments. Back- and midhaul over PON is being deployed today. As opposed to point-to-point optics, PON extends the aggregation gain into the ...access domain. We explain the steps taken in the mobile and PON industries to enable efficient eCPRI fronthaul over PON. We explain how fronthaul has evolved into a bandwidth-efficient eCPRI and what mechanisms are in place to enable coordinated scheduling decisions of the mobile and PON systems. The recent end-to-end demonstration of coordinated scheduling helps pave the way towards future industry adoption.
A time-division-multiplexed (TDM) passive optical network (PON) that behaves like multiple point-to-point (P2P) links can support applications with stringent timing requirements while also ...maintaining the cost benefits of the point-to-multipoint (P2MP) topology. This requires the TDM-PON to provide deterministic performance: lossless transmission and low and constant (with low variations/jitter) latency to selected flows, while also serving other, e.g., best-effort, traffic flows. We demonstrate two approaches for providing deterministic performance over a TDM-PON. In the first approach, we operate the PON asynchronously to its clients and use scheduling that provides upstream bursts at a low and constant period. Jitter compensator gateways (JC GWs) are used to compensate for the jitter introduced by the non-matching PON bursts and the input traffic cycles. In the latter approach, we implement a deterministic dynamic bandwidth allocation (detDBA) process that controls the placement of bursts at each PON frame for selected transmission containers (T-CONTs) that correspond to flows with given traffic profiles. We synchronize and co-schedule the PON with the rest of the network and applications to provide deterministic performance to those flows. As a use case, we study the communication of industrial applications over the deterministic PON system and demonstrate latency below 100 µs and sub-µs packet latency jitter for the industrial flows, while at the same time serving best-effort traffic flows.
Standardization activities are nearly complete for single wavelength 25 Gb/s time-division multiplexed (TDM) passive optical networks (PONs) and well underway for 50 Gb/s TDM PONs. There is ...considerable debate in the industry about which technology will be the “next step” after 10 Gb/s TDM PON, now finally starting to ramp up to mass deployment. 50 Gb/s PON clearly brings a {2} \times2× bandwidth advantage over 25 Gb/s, at least in the downstream direction. On the other hand, the increase of speed to 50 Gb/s brings with it a substantial receiver sensitivity penalty of at least 4 dB, which has a chain effect on transceiver architecture, cost, and time-to-market. In this paper, each of those elements is investigated, quantified, and compared to 25 Gb/s.
FLCS-PON is a concept of a flexible passive optical network (PON), where the modulation and coding parameters of the downstream signal, consisting of modulation order, code rate, and probabilistic ...shaping entropy, can be adjusted on a timeslot basis to opportunistically achieve mean net bitrate increase. The system harnesses unused margins of transceivers and optical distribution networks. In this work we describe the architecture of FLCS-PON, which is designed to leverage the 50G-PON ecosystem. We provide updated and accurate performance metrics for FLCS-PON low-density parity check (LDPC) forward error correction (FEC) codes. We then report on the operator trial of a FLCS-PON system prototype carried out jointly with Vodafone and demonstrate maximum achievable net bitrates as a function of the optical path loss for five different transmitter configurations (non-return-to-zero, PAM-4, and probabilistically shaped PAM-4 with three different entropy values). On the receiver side we test four different configurations: FFE23+DFE5 or FFE16+DFE1 equalizers, each followed by either a hard- or a soft-input LDPC decoder. Finally, we consider two study cases on mean bitrates achievable with FLCS-PON over deployed optical distribution networks (ODNs). We map net bitrates obtained during the operator trial to Vodafone’s actual ODN optical path loss probability distribution or an ensemble of simulated ODNs. We show that in the majority of cases, FLCS-PON can provide a significant improvement of mean net bitrate. Further, FLCS-PON also enables extension of nominal power budget classes, beyond guaranteed conventional ODN loss, making it possible to provision links that might otherwise be unsupported by conventional PON.
