Optical Access Networks Research Articles

Towards automation of fibre to the home planning with consideration on OPTIC access network model

Owing to the rapid technological evolution, tough competition and budget limitation, the service providers are struggling to provide a cost-effective solution to minimise their operational cost with extraordinary customer satisfaction. One of the factors that increase the cost of overall Fibre To The Home (FTTH) network is the unplanned deployment resulting in utilisation of extra components and resources. Therefore, it is imperative to determine a suitable technique, which helps to reduce planning process, required time and deployment cost through optimisation. With the intention to meet the increasing demand of future higher bandwidth applications, the fibre-based access is considered best resolution to deliver triple play services (voice, data, video). It is therefore preferred with great need to migrate from traditional copper-based network to fibre-based access. Automation-based planning is one of the possible ways to automate the network design at probable lowest cost. In this research, a technique for migration from copper to fibre access network with a climbable and optimised Passive Optic Network (PON-FTTx) infrastructure is proposed identifying the need for new technology in developing countries.

Motion Control System With Time-Varying Delay Compensation for Access Edge Computing

There is an increasing demand for motion control of Internet of Things devices such as drones and industrial machines from large computational resources on the network side. Since the delay between communication devices adversely affects the control performance, utilization of low-latency platforms such as edge computing is promising. However, no other study focuses on architecture and control methods in optical access network for motion control. We aim at realizing the access edge that performs real-time motion control on an edge server located in a central office. This paper proposes an access edge configuration and a control method that offers time-varying delay compensation based on delay information. We evaluate control performance of our method when delay is increased and packet loss occurs under a high network load environment. We demonstrate that when the downstream traffic changes from 9 to 10 Gbps, the proposed method offers motor control settling times of 2.7 s and 8.0 s, respectively, while the conventional method cannot control the motor in either case.

Towards automation of fibre to the home planning with consideration on OPTIC access network model

Towards automation of fibre to the home planning with consideration on OPTIC access network model

Multi Wings Chaotic Encryption Scheme for PAM-DMT-Based Optical Access Network

In this paper, we propose a novel 3-dimension multi wings chaotic encryption scheme for PAM-DMT-based optical wireless access network. In our proposed scheme, one dimension (x) is used for XOR operation, one dimension (y) is used for confusion of PAM signal's amplitude and one dimension (z) is use for DMT subcarrier scrambling. We experimentally demonstrate the 3-dimension multi wings chaotic encryption scheme in PAM4-DMT optical access network. The experimental results show that our proposed scheme can effectively enhance physical-layer transmission security and simultaneously improve transmission performance. What is more, the proposed scheme has good scalability. It can be extended to high order PAM-DMT system and can use more wings to enlarge the key space. To verify the effectiveness of the scheme for practical application, encrypted transmission of a digital image in 60 km SMMF is demonstrated.

Indoor optical wireless access networks—recent progress [Invited

Optical wireless access networks have seen rapid progress. With beam-steering capability, optical wireless communications can deliver very high capacity, support user mobility with indoor localization supported directly at the optical layer, be resilient against the blocking of beams by exploiting spatial diversity at the optical layer, and guarantee low-latency links with modified protocols and network architectures. This paper presents a review of recent progress in achieving functions of communication, localization, resiliency, and dynamic networking using optical-layer techniques.

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.

Chaotic constant composition distribution matching for physical layer security in a PS-OFDM-PON

This paper proposes a probabilistic shaping orthogonal frequency division multiplexing passive optical network (PS-OFDM-PON) based on chaotic constant composition distribution matching (CCDM). With the implementation of a four-dimensional hyperchaotic Lv system, probabilistic shaping and chaotic encryption are realized with low complexity on the process of signal modulation, so as to enhance the system performance in the presence of bit error rate (BER) and security. An 8.9 Gb/s encrypted PS-16 quadrature amplitude modulation (QAM)-OFDM signal transmission over a 25 km standard single mode fiber (SSMF) is experimentally demonstrated. And experimental results indicate that compared with conventional uniform 16QAM-OFDM, the encrypted PS-16QAM-OFDM can obtain a 1.2 dB gain in receiver sensitivity at a BER of 10-3 under the same bit rate. Moreover, the key space of the proposed scheme is 1.98 × 1073, which is a large enough number to effectively guard against any malicious attacks from illegal optical network units (ONUs). The combined superiority of BER and security performance enables a promising prospect for the proposed PS chaotic encryption scheme in a future low-cost optical access network.

Develop TE/TM Pass Filters on double-loaded-on-ridge Structure with ITO/TiN for Upstream FTTH Optical Access Networks

In this paper, TE/TM pass filters are introduced as a dual optical multiplexer in the fiber-to-the home (FTTH) uplink transmission. The architecture is implemented at 1330 nm wavelength, with a double-loaded-on-ridge structure. In the TE pass filter, TM mode couples with plasmonic mode while TE mode is guided through the core with low losses due to the effect of the two plasmonic materials. The TM mode is directed through the heart, though, in the TM pass filter. Transparent conductive oxides (TCOs) as Indium Tin Oxide (ITO), in addition to Titanium Nitride (TiN) are proposed as plasmonic materials in optoelectronics devices. TCOs possess advantages for their transparency, functionality in the NIR region, and its low real permittivity compared to other plasmonic materials. ITO/TiN combination shows better performance than single plasmonic material on the filtration process. At 1330 nm of operating wavelength, the TE-pass filter operates with an extinction ratio of 20.62 dB and an insertion loss of 0.44 dB. Moreover, the TM pass filter performs with an extinction ratio of 20.2 dB and an insertion loss of 0.36 dB. The TE and TM pass filters have a device length of 2.5 μm and 2 μm, respectively.

Integration of fiber and FSO network with fault-protection for optical access network

In this paper, we proposed and experimentally demonstrated the integration of optical fiber and free-space optic (FSO) with fault protection for the optical access network. The proposed architecture has a fault protection or self-healing function when a link failure is occurred in the network. Thus, the proposed self-healing architecture is a promising network for improved reliability and survivability of optical network especially for the remote area when the fiber is broken or cut between each remote node (RN) and optical network unit (ONU). Moreover integration of optical fiber with the FSO network is used to increase the coverage range of the broadband wireless network and improve the flexibility of the network. In the experiment, the signal is generated by using the signal generator, and propagates through a hybrid of 25 km SMF, and FSO link and then transmitted into each ONU. Finally, we compare and evaluate the signal transmission performance of channels in terms of bit error rate (BER) and error vector magnitude (EVM) after back-to-back (BTB) transmission, 25 km SMF transmission, and after a hybrid of 25 km SMF with FSO link transmission. The experimental result proves that the hybrid of 25 km SMF with FSO link increases the communication coverage range with a reasonable performance.

Performance analysis of erbium-doped fiber amplifier (EDFA) and hybrid optical amplifier in NG-PON2 based on TWDM-PON system

One of the milestones in the optical access network evolution is the Next-Generation Passive Optical Network Stage 2 (NG-PON2) that has 40 Gbps as minimum upstream/downstream capacity. The optical amplifiers have to implement to combat the power degradation in the transmission line. This research aims to analyze the performance of EDFA boosters and hybrid optical amplifiers, which are implemented on TWDM-PON systems based on NG-PON2. Our work used 80 Gbps data speed, which each channel had 10 Gbps on eight channels with a channel space of 100 GHz. The optical link used in this simulation was 60 km with the Erbium-Doped Fiber Amplifier (EDFA) and Hybrid Optical Amplifier (HOA). The performance analysis is based on the variation of ONU and amplifier. Based on the results, the best value in the downstream is the transmission line using EDFA with the received power of - 19.184 dBm, Q Factor of 7.975, and BER of 5.852 x 10−16. In upstream transmission, the best value obtained was a hybrid optical amplifier with a received power value of 9.025 dBm, Q Factor of 69.64, and BER of 0. The optical amplifier increased the system performance when implemented on TWDM-PON systems based on NG-PON2.

A Review on MIMO Wireless Signals over Fibre for Next Generation Fibre Wireless (FiWi) Broadband Networks

Next-generation access/mobile networks have set high standards in terms of providing wireless services at high data rates in order to keep up with the vast demands for other mobility and multiple services. Wireless-optical broadband access network (WOBAN) technology, also known as fibre-wireless (FiWi), has uncovered incredible opportunities for the future of next-generation networks because it gets the best of both domains: huge bandwidth provided by the optical fibre and high ubiquity of the wireless domain. The objective of FiWi networks is to integrate the high data rate and long reach provided by optical networks and the ubiquity and mobility of wireless networks, with the target to decrease their expense and complexity. Multiple-input–multiple-output (MIMO) is an inevitable technique for most of the new mobile/wireless networks that are driven by the huge data rates required by today’s users. Consequently, to construct any FiWi system for next-generation (NG) access/broadband networks, an MIMO technique has to be considered. This article presents a comprehensive, contemporary review of the latest subsystems, architectures and integrated technologies of MIMO wireless signals backhauling using optical fibre or fibre access networks, such as passive optical networks (PONs). An overview for FiWi, PONs and MIMO wireless systems is provided. In addition, advanced techniques of accommodating the MIMO wireless signals over optical fibre are explained and compared. Different types of wireless MIMO signals over fibre, such as 5G, WiFi and related transport technologies, are reviewed. Moreover, future research trends are also discussed.

Fiber to the Home (FTTH) Automation Planning, Its Impact on Customer Satisfaction & Cost-Effectiveness

The use of automated network planning systems is crucial for reducing the deployment cost and planning time of passive optical telecommunication networks. Mixed-integer linear programming (MILP) is well suited for the purpose of modeling passive optical networks; however, excessive computing times for solving large-scale problem instances render these approaches impractical. This research presented a formulation that was based on MILP. It is for the issue of optimum dimensions of fiber equipment of the FTTH optical-access network (FTTH-OANs). The key objective is to minimize the capital expenditure associated with the implementation of FTTH-OAN, i.e. the expense of passive and active tools (splices, fiber terminations, closures, cables, optical splitters, and OLT cards, etc.) site planning costs and the cost of labor needed. This formulation is installed and tested. The key results are derived from practical physical systems installed in homes.

Investigation of 340-Gbps terrestrial FSO link incorporating spectral-efficient DP-QPSK-PolSK hybrid modulation scheme

A high-capacity spectral-efficient dual-polarization quadrature phase-shift keying (DP-QPSK)-polarization shift-keying (PolSK) hybrid modulation scheme for terrestrial free-space optics (FSO) transmission link is proposed and investigated. A DP-QPSK signal modulated at 300 Gbps and a PolSK signal modulated at 40 Gbps are simultaneously transmitted using a single optical carrier over the FSO link. The proposed link performance is investigated under different weather conditions, where the bit error rate metric is used to evaluate the performance of the PolSK modulated signal and the error vector magnitude parameter is used for the DP-QPSK signal. The FSO link range and the required received power are carefully explored. The conducted numerical simulations of the proposed system showed reliable 340-Gbps data transmission over link ranges varying from 1.6125 to 50 km depending on the weather conditions. The impact of the channel scintillation due to atmospheric turbulence is also investigated. The proposed high-speed FSO transmission system offers a promising solution for high-bandwidth hungry systems used for the internet of things, 5G, and smart cities. It can also be used in developing fronthaul/backhaul links for future wireless networks and optical access networks. The performance of the proposed transmission system is compared with recently published work in the literature.

Digital-Analog Hybrid Optical Access Integrating 56-Gbps PAM-4 Signal and 5G mmWave Signal by Spectral Null Filling

A bandwidth-efficient and low-cost spectral-null-filling scheme simultaneously delivering a 56-Gbps 4-level pulse amplitude modulation (PAM-4) digital signal and a 10 × 400-MHz analog radio frequency (RF) signal on a single wavelength is demonstrated for high-capacity wired and wireless optical access networks. The data rate of the PAM-4 signal is consistent with the next-generation passive optical network (PON), and the PAM-4 signal inherently provides a spectral null at 28 GHz, which can be filled with the RF signal exactly at the 5G-specified millimeter wave (mmW) band. Since pulse shaping is not essential in this hybrid transmission system, a low-cost 2-bit digital-to-analog converter (DAC) is adopted for the PAM-4 signal generation. Volterra nonlinear equalizer is adopted to effectively eliminate the analog-to-digital crosstalk without reserving a frequency gap in between. The digital-analog hybrid signal is simultaneously transmitted over a 25-km standard single-mode fiber in telecom C-band and the impact of chromatic dispersion on the number of supported mmW bands is analyzed. In addition, three types of hybrid transmitters are experimentally demonstrated, among which the first-time proposed IQ-modulator-based hybrid transmitter shows the best performance.

Bounds and constructions for multilength variable-weight optical orthogonal codes

Multilength variable-weight optical orthogonal codes (MLVWOOCs) are recently proposed for supporting multirate and integrated multimedia services in optical code division multiple access (OCDMA) networks. In this paper, we consider (N,M,W,1,Q;λ)-MLVWOOCs with λ=2 (the minimum nontrivial intercross-correlation). Some upper bounds on code size are obtained under certain restrictions, an (N,M,W,1,Q;λ) compatible difference packing (CDP) set system is introduced to construct an MLVWOOC, and an equivalence relation between a CDP set system and an MLVWOOC is established. Recursive constructions for MLVWOOCs are also presented. By using cyclotomic classes, disjoint skew starters and recursive constructions, infinite classes of MLVWOOCs with W={3,4} and λ=2 are obtained which are of optimal sizes reaching the upper bounds.

Highly Reliable Transmission System for Next-Generation Optical Access Network Based on Silicon Modulator With Maximum-Ratio Combined Receiver

A novel maximum-ratio combined receiver (MRC-RX) is proposed and demonstrated through a proof-of-concept experiment, conducted to mitigate the system performance degradation caused by the low linearity of the silicon modulator when deployed in passive optical network (PON)-based access. By employing the proposed MRC-RX, an optimized receiver sensitivity is achieved, which enables the mitigation of the performance degradation induced by the silicon modulator, and a more reliable transmission in both cases of low and high received power. In the proof-of-concept experiment, at a bit error rate of 1.0 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> , the receiver sensitivity of the MRC-RX was improved by 3.5 dB and 6.7 dB compared with the lite coherent receiver (lite CO-RX) and direct detection receiver (DD-RX), respectively. Compared with a system employing a commercial lithium niobate (LiNbO3) modulator, a maximum improvement of ~5.6 dB in the receiver sensitivity was obtained for the MRC-RX in the silicon modulator system. Thus, the system performance degradation caused by the low linearity of the silicon modulator can be effectively reduced by employing the MRC-RX. The proposed method makes sense to the building of next generation high reliable photonics integrated access by employing silicon modulators.

Bidirectional Transmission in TWDM Optical Access Network with Tunable Wavelength ONU

In this paper, a novel configuration for bidirectional hybrid time and wavelength division multiplexing (TWDM) optical access network is presented that fulfills the growing broadband requirements of next generation 5G customers. A purely passive system module is suggested for 512 subscribers that can communicate at a line rate of 240 Gbps in downlink and 160 Gbps in uplink over the common fiber cable. Shared network infrastructure helps in amortization of the installation and recurring operational expenses. Subscriber optical network unit (ONU) consists of tunable wavelength transmitter that can adjust uplink channel on the instructions of the medium access control layer (MAC). Improved Bandwidth Optimization Hybrid Scheduling Algorithm (BOHSA1) is implemented in the network to reduce the wastage of time slots per channel that helps in improving the channel utilization. The demonstrated architecture is extensively investigated to know the impact of diverse encoding scheme; photo-detector and electric filter have on the network performance.

Probabilistically shaped amplitude and pulse position modulation based on stepped amplitude probability distribution for optical access networks

AbstractWe propose a novel probabilistically shaped amplitude and pulse position modulation (APPM) based on stepped amplitude probability distribution for optical access networks. By adopting the probabilistic shaping (PS) technique, average signal power can be reduced and better bit error rate (BER) performance obtained. The proposed PS‐APPM scheme has been successfully verified in a 25‐km standard single‐mode fiber (SSMF). Experiment results show that at a BER of 1 × 10−3, the proposed 4 × 16 APPM‐PS1 and 4 × 16 APPM‐PS2 outperform the traditional 4 × 16 APPM by 1.54 and 2.52 dB receiver sensitivity improvement, while the proposed 8 × 8 APPM‐PS1 and 8 × 8 APPM‐PS2 excel the traditional 8 × 8 APPM by 2.1 and 3.5 dB at a BER of 1 × 10−2, suggesting the advanced nature of the proposed scheme for future optical access networks.

Resilient architecture for optical access networks

This work proposes a resilient wheel-based wavelength-division-multiplexed passive optical network optical access network architecture for backhauling network traffic. This proposed resilient architecture can efficiently support not only the fixed users but also the mobile users in the downstream direction under normal and failure operating scenarios, while minimizing the average traffic delivery time and without using extra redundant fibers for protection purposes.

Extended L-band monolithically tunable InAs/InP quantum-dash multimode laser with integrated amplifier

A two-sectioned InAs/InP quantum dash laser structure is proposed and investigated as a monolithic broadband multimodal tunable laser with an integrated semiconductor optical amplifier. The optical power-injection current and spectral characteristics of the device at different operating conditions demonstrated a total wavelength tunability of ∼15.8 nm in the extended-L-band (∼1615 to ∼1630.8 nm) window with ∼2.0 times −3 dB bandwidth enhancement. Furthermore, due to the unique tunability mechanism of forward biasing the amplifier section, the device exhibits simultaneous wavelength tuning as well as optical amplification features, with an estimated gain of ∼8.5 dB affirmed by an increase in the wall-plug efficiency up to 6.8% from 3.9%, shown by its single-section counterpart. This demonstration paves a potential platform for the deployment of broadband quantum-dash laser-amplifiers as unified light sources in next-generation optical access networks.