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Only radio access networks can provide connectivity across multiple antenna sites to achieve the great leap forward in capacity targeted by 5G. Optical fronthaul remains a sticking point in that connectivity, and we make the case for analog radio over fiber signals and an optical access network smart edge to achieve the potential of radio access networks. The edge of the network would house the intelligence that coordinates wireless transmissions to minimize interference and maximize throughput. As silicon photonics provides a hardware platform well adapted to support optical fronthaul, it is poised to drive smart edge adoption. We draw out the issues in adopting our solution, propose a strategy for network densification, and cite recent demonstrations to support our approach. [ABSTRACT FROM AUTHOR]

In the 5G era, optical fronthaul is a major challenge in meeting growing demand. Edge computation and coordinated multipoint for 5G have stringent requirements for high throughput and low latency, either in single-wavelength or wavelength-division-multiplexing fronthaul. We propose a new silicon photonic solution to deliver 5G services on existing optical access networks with colorless optical network units, such as passive optical networks. The newly added 5G services form a heterogeneous optical access network. Using the existing fiber infrastructure, broadband services coexist with new 5G signals that can densify 5G coverage. The proposed scheme is both wavelength-selective (in the distribution network) and colorless (at the end user site). We use silicon microring modulators to create subcarriers slaved from the broadband service distributed carrier; additional microring modulators generate 5G signals exploiting those subcarriers. We experimentally validated the successful coexistence of 5G signals (various formats) with a broadband signal (various formats). [ABSTRACT FROM AUTHOR]

We propose for the first time to use a silicon photonics (SiP) solution for a passive optical network to both reduce signal-signal beat interference (SSBI) and recuperate a part of the downlink carrier for use in the uplink. The Kramers–Kronig (KK) receiver for direct detection of advanced modulation formats overcomes SSBI at the cost of a moderate carrier to signal ratio ($>$ 6 dB) and high oversampling (4×). We propose an optical SSBI solution that achieves better performance than KK and requires only standard sampling and low (3 dB) carrier to signal power ratio. The receiver is conceived for the downlink in passive optical networks, where carrier signal must be husbanded for re-use in the uplink. Using cost effective and power efficient SiP, the receiver filters the incoming signal, suppresses SSBI, and routes a portion of the carrier for use in the uplink. We experimentally examine the SSBI suppression in this paper. While previous demonstrations used bulky, discrete components, we achieve significant Q-factor improvement with a simple SiP solution. We examine the optimal frequency offset between the carrier and the microring resonator center frequency. The robustness to frequency drift, as well as the impact of imperfect filtering, is discussed and quantified. [ABSTRACT FROM AUTHOR]

We propose and experimentally demonstrate a carrier-reuse,single-feeder,wavelength-division-multiplexed, orthogonalfrequency-division-multiple-accesspassiveoptical network (WDM-OFDMA-PON) with colorless direct-detection optical network units and coherent detection optical line terminals. We examine two strategies by adjusting the frequency occupancy and the modulation format of the uplink (UL) and downlink (DL) signals. We investigate the impact of the DL signal-to-carrier ratio on the performance of both the UL andDLsignals via simulations and identify impairments limiting system performance. As a proof of concept,we demonstrate on a single wavelength channel a realization of each of the two scenarios investigated using orthogonal frequency division- multiplexing (OFDM). A quadrature phase-shift keying approachwith a wide spectrum and a narrow guard band achieves 21.6 Gb/s.A32-aryquadrature amplitudemodulation approach with a narrow spectrum and a wide guard band achieves 14.5 Gb/s and a span of over 80 km. [ABSTRACT FROM PUBLISHER]

We present a simple, straightforward technique to enable bidirectional transmission of analog and digital signals in single-fiber wavelength division multiplexing passive optical network systems employing reflective semiconductor optical amplifiers (RSOA). An On-Off-Keying (OOK-DL) downlink modulation is effectively erased in a saturated RSOA, reflecting a carrier for retransmitting on the same fiber an in-band analog WiFi orthogonal frequency division multiplexing uplink signal (OFDM-UL). We investigate the operating conditions and the optimization procedure to attain required signal quality for both the uplink and downlink. We demonstrate experimentally the maximum distance and the best attainable performances for different lengths of standard single mode fiber (transmission). Bit error rate below the forward error correction threshold is obtained for WiFi OFDM-UL signal over 40 km and up to 80 km of SSMF using 64QAM and QPSK modulation modes, respectively. In all cases, we achieve error-free operation for the OOK-DL signal at 1 Gb/s. [ABSTRACT FROM PUBLISHER]

As PONs carry increasing amounts of data, issues relating to their protection and maintenance are becoming crucial. In-service monitoring of the PON?s fiber infrastructure is a powerful enabling tool to those ends, and a number of techniques have been proposed, some of them based on optical time-domain reflectometry. In this work we address the required features of PON monitoring techniques and review the major candidate technologies. We highlight some of the limitations of standard and adapted OTDR techniques as well as non- OTDR schemes. Among the proposed opticallayer monitoring schemes, we describe our novel optical-coding-based reflection monitoring proposal and report on recent progress. We end with a discussion of promising solution paths. [ABSTRACT FROM PUBLISHER]

We evaluate the theoretical performance of recently proposed optical coding (OC) technology for fiber fault monitoring of a PON through the signal-to-noise ratio (SNR), the signal-to-noise-plus-interference ratio (SNIR), and the false-alarm probability. First, we develop a mathematical model and expressions for the detected monitoring signals considering a square law detector and using realistic parameters. Second, we address the effect of the transmitted pulse power, network size and light source coherence on the performance of both one-dimensional (1D) and two-dimensional (2D) OC monitoring systems. We show that the transmitted pulse width can be optimized to trade-off the interference and the detection noises. We give simple analytic equations for this optimal pulse width as a function of network parameters. Both 1D and 2D coding schemes are considered. We find that, under perfect dispersion compensation, an incoherent source performs better than lasers for 1D coding. In addition, 2D coding using lasers offer very good performance and supports networks up to 128 customers with SNIR≥10dB; a promising candidate for future high capacity PON. Finally, we apply Neyman-Pearson testing to the receiver of our monitoring system and investigate how coding and network size affect the operational expenses (OPEX) of our monitoring system. [ABSTRACT FROM AUTHOR]

We analyze the performance of fiber fault monitoring of a PON using a centralized, passive optical coding (OC) system. We develop an expression for the detected monitoring signal, study its statistics, and contrast our OC monitoring system with standard optical code division multiplexing (OCDM) data communication. We derive a new closed form lower bound expression for the interference probability, and use this to find the signal-to-interference ratio (SIR). A service provider cannot control the physical layout of homes in a coverage area; measuring performance for one network layout would be insufficient to test our proposed monitoring system. Client geographic distribution has a significant impact on the SIR. We consider five different PON geographical distributions and study their effect on OC monitoring performance. Our results show that SIR is sufficient to successfully monitor the network. In addition, we find that the uniform radial (UR) distribution, an analytically tractable distribution, gives good performance estimation and can therefore be a useful tool in characterizing performance in terms of both SIR and signal-to-noise ratio (SNR). [ABSTRACT FROM AUTHOR]

In this letter, we propose a novel optical coding scheme for fiber link quality monitoring of a passive optical network (PON). The proposed scheme named incrementally pulse positioned coding (IPPC) is practically very attractive due to its simple design and fabrication process, small size, zero coding loss and low cost. We demonstrate the superior correlation properties of IPPC over existing codes, address the design considerations, and evaluate its performance for a PON monitoring system via the average signal-to-interference ratio (SIR). [ABSTRACT FROM PUBLISHER]

We propose and experimentally demonstrate generation and distribution of optimally power efficient impulse-radio ultra-wideband (IR-UWB) waveforms over passive optical networks (PONs) for high bit rate wireless data distribution in the home. We use a reconfigurable UWB pulse generator in the context of radio over fiber delivery over a PON for fiber to the home/premises services. The single mode fiber PON feeder is used to create the required dispersion for the frequency-to-time conversion for optical pulse shaping. As the feeder length varies for different PONs, a tunable UWB pulse generator compensates for variable dispersion. We can compensate the effect of feeder length over a high dynamic range. We experimentally demonstrate the generation of the same UWB pulse for feeder lengths of 17, 27.5 and 35.5 km by tuning the optical pulse generator. [ABSTRACT FROM AUTHOR]

We investigate experimentally and via simulation, the monitoring of fiber link quality in a PON using optical coding technology. We discuss design issues for periodic coding and the optimal detection criteria. We develop a reduced-complexity maximum-likelihood sequence estimation (RC-MLSE) algorithm. We conduct experiments to validate our detection algorithm using four periodic encoders that we designed and fabricated. Error-free detection is confirmed for encoders with separation as small as 1 m. Using the experimental data for the encoder impulse responses, we conduct Monte Carlo simulations for realistic PON geographical distributions with randomly located customers, again with error-free detection. We investigate the effect of coverage area and network size (number of subscribers) on the computational efficiency of our algorithm. We provide a bound on the probability that any given network will cause the algorithm to take exorbitant time to monitor the network, i.e., the time-out probability. Finally, we highlight the importance of averaging to remedy the power/loss budget limitations in our monitoring system to support higher network sizes and longer fiber reaches. [ABSTRACT FROM PUBLISHER]