Wavelength Division Multiplexing Passive Optical Network Research Articles

40 Gb/s wavelength division multiplexing-passive optical network (WDM-PON) for undersea wireless optical communication

Abstract We demonstrate the design and simulation of a long range four-channel wavelength division multiplexing-passive optical network (WDM-PON) operating at 40 Gb/s (4 × 10 Gb/s) in downstream transmission for undersea wireless optical communication. The proposed model consists of two separate subsections between the optical transmitter and receiver. The first subsection consists of the central office and 50 km long feeder fiber for transmitting the optical signal from a distant base station to the 1 × 4 optical demultiplexer located at the sea shore. The second subsection comprises 500 m distributed fiber from the 1 × 4 optical demultiplexer to the terminal point placed at the bottom of the sea and 15–20 m optical wireless channel inside sea water. Simulation results confirmed successful transmission of optical signals from the 50 km distant optical transmitter to the optical receiver located maximum 15 m inside the sea water with a signal-to-noise ratio of ∼20.96 dB, bit error rate of ∼1.55 × 10−8, and quality factor of ∼5.584. The eye diagram at the receiving end also exemplifies quality downstream data transmission at a rate of 10 Gb/s per channel. In addition, we compare the simulation results of the four-channel 40 Gb/s WDM-PON system with a four-channel WDM-PON system operating at 4 Gb/s (4 × 1 Gb/s). Simulation results confirm maximum reach of 17.5 m inside sea water at a cost of significant reduction in data rate. Furthermore, we analyze the system availability of the proposed WDM-PONs and find convincing results for high-speed secured data transmission under water.

A hybrid next-generation passive optical network and visible light communication for future hospital applications

The advancement in the latest healthcare technologies have shown a growing interest in 10/10 Gbps per channel hybrid next generation passive optical network (NG-PON) and visible light communication (VLC) networks to achieve the aim of future hospital applications. This paper investigates the use of hybrid time and wavelength division multiplexing PON (TWDM-PON), wavelength division multiplexing optical code division multiple access PON (WDM-OCDMA PON) using zero cross-correlation (ZCC) code and VLC for the hospitals scenario. The proposed bidirectional system is investigated for four TWDM, six WDM-OCDMA and three VLC information channels in terms of variable fiber length, bit rate, different OCDMA codes and multi-hospital systems. It is investigated that upstream channels performs better than downstream channels and provides the successful 10/10 Gbps hybrid system over 50 km fiber and 10 m VLC link serving 53 users in single hospital system. It also provides the high eye-height, optical signal to noise ratio (OSNR) and received power. Moreover, the performance of the proposed system can be further enhanced by using modified quadratic congruence (MQC) code and high transmission power. Also the comparative analysis with existing systems show the superiority of the hybrid NG-PON/VLC system using fiber/wireless links over the conventional radio access networks in healthcare applications.

Single mode fiber-free space optic based hybrid $$32\times 2~\text{Gbps}$$ WDM-PON architecture employing optical frequency comb source and polarization multiplexing

In this paper, we propose a cost-efficient single mode fiber-free space optics (SMF-FSO) based hybrid $$32 \times 2~\text{Gbps}$$ wavelength division multiplexed passive optical network (WDM-PON) employing optical frequency comb (OFC) source and polarization multiplexing. OFC source is realized at optical line terminal (OLT) by modulating a single continuous wave (CW) laser source with radio frequency (RF) sinusoidal signal and dual-drive Mach–Zehnder modulator (DD-MZM). 16 coherent optical carriers are used to split into 32 x and y-orthogonal polarization states which are used to transmit the on-off keying (OOK) data of 32 channels to remotely located optical network units (ONUs). The performance of the channels is analyzed with bit error rate (BER) plots employing Gamma–Gamma (GG) FSO channel model at different turbulence regimes and lengths of FSO link. Moreover, the effect of varying the polarization mode dispersion (PMD) on BER is also evaluated. The cost of the proposed architecture is analyzed and compared with conventional PON architecture. The cost efficiency of the proposed architecture is demonstrated by the use of a single CW laser source to transmit the data of 32 users between remote node (RN) and ONUs through FSO links having reduced installation and maintenance costs.

25 Gb/s Data Transmission Using a Directly Modulated InGaAlAs DBR Laser over 14 nm Wavelength Tuning Range

With the deployment of the fifth generation of mobile networks (5G), 25 and 100 Gb/s directly modulated lasers and modules will become the mainstream optical transmitters. A directly modulated InGaAlAs/InP distributed Bragg reflector (DBR) laser is fabricated by butt-joint technology. A 25 Gb/s data transmission over a single-mode fiber of up to 10 km is demonstrated, and a wavelength tuning range of 14.28 nm is achieved through injection current tuning of a DBR section and temperature control of a thermoelectric cooler (TEC), which is the best candidate of colorless light sources for wavelength-division-multiplexed passive optical network (WDM-PON) systems.

8 × 10 Gb/s Downstream PAM-4 Transmission for Cost-Effective Coherent WDM-PON Application

We experimentally demonstrate digital signal processing (DSP)-free 8 × 10 Gb/s 4-level pulse-amplitude modulation (PAM-4) transmission for cost-effective coherent wavelength division multiplexing passive optical network (WDM-PON) with 20 GHz channel spacing over the C-band. The polarization-independent coherent receiver at optical network unit (ONU) including a 3 × 3 fiber coupler and a polarization beam splitter (PBS) followed by three single-ended photodiodes (PDs), is simple and cost-effective, because neither DSP nor phase/frequency locking is necessary for the coherent detection of PAM-4 signal. We numerically compare the performance between the transmitted signal diversity and the local oscillator (LO) signal diversity schemes, and optimize the parameters of heterodyne detection, in order to enhance the power budget. Based on the LO signal diversity scheme, we can achieve an average receiver sensitivity of -26 dBm for eight wavelength channels at a bit error ratio (BER) below the hard-decision forward error correction (HD-FEC) threshold (i.e., 3.8 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> ), leading to a power budget of 29 dB after 25 km standard single-mode fiber (SSMF) transmission. Moreover, we verify an unequally spaced PAM-4 signaling, leading to contribution of 1 dB receiver sensitivity improvement for 10 Gb/s/λ PON.

Performance Analysis of a Full-Duplex TWDM-PON Using OFDM Modulation with Red LED Visible Light Communication System

Today’s access networks are in high demand to fulfill the high bandwidth requirement because of extensive improvement in high transmission rate applications for cloud computing, big data analytics, and other next-generation 5G smart applications. In this work, the symmetrical and bidirectional time and wavelength division multiplexing-passive optical network (TWDM-PON) system is proposed and demonstrated. Orthogonal frequency division multiplexing (OFDM) with 4-level quadrature amplitude modulation is used for downstream and upstream transmission. Also, 625 nm red light-emitting diode is utilized for visible light communication (VLC) using a wireless link to encourage the economic high transmission rate fiber/VLC optical network. The TWDM-PON employing OFDM with the VLC system has been analysed for downstream and upstream channels for variable fiber-wireless link range. Additionally, the impact of a high transmission rate and usage of digital signal processing (DSP) unit to reduce losses due to fiber nonlinearity effects in the proposed link has been investigated. The results show that the maximum faithful wireless and wired range for the proposed system is 140 m and 60 km respectively at 20 Gbps to attain the minimum 3.8 × 10−3 BER. The decrease in error vector magnitude (EVM%) by almost 52% with the use of DSP in the proposed system provides a high transmission rate of 200 Gbps in the proposed link. Further, comparative performance of the proposed system with previous latest works in literature reveals a superior performance of the proposed link. The proposed TWDM-PON system provides a next-generation access network from rural areas to urban areas.

Simultaneous transmission of clock and data signals in photonic-assisted WDM passive optical networks

This work reports on the use of a gain-switched vertical cavity surface-emitting laser (VCSEL) optical frequency comb (OFC) to generate multiple optical carriers for applications in future wavelength-division multiplexing (WDM) passive optical network (PON) systems. The VCSEL-based OFC system was tested for its ability to simultaneously transmit error-free data signals up to 30 Gbps, and a 50 MHz clock signal proposed to be used for latency monitoring of the network. The system was demonstrated over a fiber distance beyond 20 km. Four optical carrier signals were filtered from the generated OFC. Three of the four optical carriers were combined and amplitude-modulated with 5 and 10 Gbps on–off keying (OOK) data signals. The fourth optical carrier was amplitude-modulated with a 50 MHz clock signal. These four modulated optical carriers were multiplexed and transmitted over 21 km of standard single-mode fiber. When the three data-carrying optical carriers were modulated with 5 Gbps OOK data and multiplexed with the clock-carrying carrier, a negligible transmission penalty was achieved after fiber transmission. When these three data-carrying optical carriers were modulated with 10 Gbps OOK data and multiplexed with a clock-carrying carrier, a maximum transmission penalty of 4.8 dB was achieved after fiber transmission. The system was investigated at a minim bit error rate (BER) of 10 − 9 . A receiver sensitivity of less than − 11 d B m was achieved at both bit rates. The clock signal suffered little effect when transmitted with the three optical carriers at both 5 and 10 Gbps data rate. A power penalty of 15.37 dB, mainly due to fiber attenuation, was experienced in the clock after fiber transmission. Due to the unavailability of the numerical system to quantify the clock performance in terms of phase noise, the phase-noise results could not be provided. Nevertheless, the provided qualitative results were able to show that the transmitted clock integrity was able to be retained after being multiplexed with transmission on the 21 km fiber channel. For the first time, to the best of our knowledge, we have simultaneously reported on data and clock transmission results using a low-power, VCSEL-based OFC to realize a WDM-PON system. These results are attractive as they demonstrate and motivate the possibility of using gain-switched VCSELs as OFC sources in future WDM-PON networks requiring enhanced channel capacity and stringent network latency monitoring to realize intelligent, simple, and power-efficient PON networks.

Performance of different hybrid dispersion compensation modules (DCMs) in long reach ultra dense WDM passive optical networks

Abstract Long reach Passive optical network (LR-PON) is an attractive solution to fulfill the ever-increasing bandwidth requirements due to propelling internet applications and competent to serve distant optical network units (ONUs). Wavelength division multiplexed (WDM) PON systems experience distance and performance limiting constraint termed as Dispersion. In order to compensate dispersion effects, Fiber bragg gratings (FBGs) and Dispersion compensation fibers (DCFs) are incorporated extensively in PONs. Performance of DCF is better than FBG in terms of dispersion compensation, but it comes at the cost of 3 $/m (very expensive). Therefore, long reach ultra dense WDM-PON systems are needed with incorporation of economical and high performance DCMs. Three newly constructed hybrid DCMs are investigated such as FBG-DCF (module 1), OPC-DCF (module 2), and FBG-DCF-OPC (module 3) in WDM-PON to get optimal DCM in terms of dispersion compensation efficiency (DCE) and economical operation. As per author’s best knowledge, DCE calculations and performance enhancement with cost reduction using hybrid DCMs in ultra dense WDM-PON, is not reported so far. WDM-PON consists of 32 channels at 25 GHz channel spacing is analyzed for 300 km link distance at 10 Gbps/channel using different hybrid DCMs. It is perceived that highest DCE of 70% is given by module 3 with maximum cost reduction of 19.84%. DCE performance of three modules is as follows: Module 3 (DCE 70%), Module 1 (DCE 55%), Module 2 (DCE 45%) and cost reduction/increase from conventional module by 19.84% reduction (Module 3), 19.05% reduction (Module 1), and increase 10.5% (Module 2). Hence, Module 3 is preferred for long reach WDM-PON to get high performance with lesser cost.

Three-Port Dual-Wavelength-Band Grating Coupler for WDM-PON Applications

Grating coupling is a widely adopted strategy for coupling light into optical waveguides. While this versatile approach benefits both fabrication and alignment, grating couplers are particularly sensitive to both wavelength and polarization. These drawbacks hinder its application in integrated wavelength-division-multiplexing passive optical network (WDM-PON) transceivers, where widely separated wavelength bands are utilized for upstream and downstream signals. In this letter, we propose a three-port grating coupler that enables polarization-independent receiving for the downstream signal from fiber and single-polarized coupling of the upstream signal from chip. Dual-wavelength-band operation is obtained by adding an output port to couple upstream wavelength on existing polarization-splitting grating coupler for downstream wavelength. Peak coupling efficiencies of -2.93 dB and -3.50 dB are achieved for 1266 nm and 1481 nm respectively. This grating coupler design can be adopted in transceivers for fiber-to-the-home (FTTH) networks.

IM/DD WDM-PON Communication System Based on Optical Frequency Comb Generated in Silica Whispering Gallery Mode Resonator

This article reports an implementation of a microsphere-based optical frequency comb (OFC) generator for substitution of individual laser arrays and simulates wavelength division multiplexed passive optical network (WDM-PON) based on this OFC generator. Our proposed generator is built based on silica microsphere, barely studied for fiber optical communication systems, and is a promising solution with photonic integration capability. Kerr OFC as a multiple light source containing more than 20 spectral carriers in the fundamental mode family in the C-band and beyond is demonstrated experimentally. Four of these OFC generator carriers with the highest peak power are studied in simulated 4-channel 393 GHz spaced WDM-PON. Additionally, we show this OFC as a source of optical carriers capable of providing data transmission over most utilized fiber types in modern optical communication systems, namely, single-mode fiber (SMF), non-zero dispersion-shifted fiber (NZ-DSF), and cut-off shifted fiber (CSF). We show through the simulations that error-free data transmission is possible, providing a total transmission capacity of 40 Gbit/s by using four OFC generated carriers.

Symmetry 28 Gbps/λ WDM Access Network Together With Confidential Connection Between Two Specific Clients

In this work, we demonstrate a symmetry 28 Gbps/ $\lambda $ on-off keying (OOK) wavelength-division-multiplexing passive optical network (WDM-PON) architecture together with confidential connection between two specific optical network units (ONUs). The presented PON access network also can prevent the Rayleigh backscattering (RB) induced interference noise. Here, to avoid re-deployment of optical fiber and increase cost, a ring-based fiber connection is proposed to connect each ONU for personal information link, when the data connection between two ONUs can be changed arbitrarily. Moreover, the corresponding signal performances of the presented WDM-PON system are also studied and discussed.

A Simple WDM-PON Architecture Together With Private Interconnected ONUs

In this paper, we present and investigate a wavelength-division-multiplexing passive optical network (WDM-PON) with symmetrical 28 Gbit/s on-off keying (OOK) access signals and 3 Gbit/s virtual private network (VPN) link between the optical network units (ONUs) simultaneously. To achieve the VPN connection, a ring-based network architecture is designed to link every ONU. Here, a direct modulation laser diode (LD) of 1311.6 nm wavelength is applied in ONU for VPN transmission to separate from PON network. In the investigation, the fiber and free space optical communication (FSO) based connections are also exploited to connect every ONU. In addition, the corresponding signal behaviors of WDM-PON and VPN networks are also analyzed and discussed.

Polarization-Discriminated RSOA–EAM for Colorless Transmitter in WDM–PON

The integrated reflective semiconductor optical amplifier (RSOA) and electro-absorption modulator (EAM) is viewed as an appealing solution to the colorless transmitter on the optical network unit (ONU) side of wavelength-division multiplexed (WDM) passive optical networks (PONs), for its broad modulation bandwidth and high optical gain. However, the conventional RSOA–EAM usually exhibits a poor upstream signal eye-diagram because it can hardly simultaneously saturate the downstream signal and boost the upstream signal as required. By exploiting the polarization-depended RSOA gain, we propose a polarization-discriminated RSOA–EAM to improve the quality of the upstream signal eye-diagram. In this device, the transverse electric polarized downstream signal is saturated by the high gain in the RSOA active region made of compressively strained multiple quantum wells, whereas the upstream signal is linearly amplified after polarization rotation. We find that, as the quality of the upstream signal eye-diagram improves with an increased polarization rotation angle, its power drops, which indicates that there exists an optimized rotation angle to reach a compromise between the upstream signal integrity and power. Simulation results show that the dynamic extinction ratio and output power of the upstream signal can reach 8.3 dB and 11 dBm, respectively, through the proposed device with its rotation angle set at an optimum value (80°), which exceeds the specification (6 dB and 4 dBm) of the upstream transmitter as required by the next-generation PON stage two. The quality of the upstream signal eye-diagram measured in Q-factor is improved by 10 dB compared to the conventional RSOA–EAM design without polarization rotation introduced.

Optical Reflection Interference Equalization for Single-Wavelength Bidirectional WDM-PON Transmission System

This paper proposes a novel return light cancellation technique using an adaptive interference equalizer in the wavelength division multiplexed passive optical network (WDM-PON) transmission system employing the single-wavelength bidirectional transmission scheme. In this scheme, the same wavelength is assigned to both the uplink and the downlink. In other words, the number of the wavelengths allocated to optical network units can be half compared with a typical PON system. However, this presents us with a problem in that the reflected component of the transmitted signal light interferes with the received signal light. We investigated the performance of the proposed interference canceling equalizer using back-to-back transmission simulation and a dual-polarization-quadrature-phase-shift-keying signal transmission experiment. The results indicated that the proposed adaptive equalizer enabled reception with no error when the OSNR was sufficiently large, even when the power of the interfering light was large (i.e., SIR ≳ 2 dB).

Liquid crystal filter based tunable transmitter for 25Gps wavelength division multiplexing-passive optical network fronthaul.

A novel tunable transmitter structure based on liquid crystal filter, to the best of our knowledge, is presented. The structure is designed for application to 5G fronthaul and supports 25 Gbps dense wavelength division multiplexing (WDM) transmission and tunable range of 35 nm. The design takes into account easy change of operation band over coarse WDM grid. Prototype samples are developed to test feasibility of the design.

Performance analysis of high speed backward compatible TWDM-PON with hybrid WDM–OCDMA PON using different OCDMA codes

In this paper, a backward compatible bidirectional 160/40 Gbps time and wavelength division multiplexing-passive optical network with hybrid wavelength division multiplexing optical code division multiple access PON (WDM–OCDMA PON) has been proposed. Six OCDMA codes have been used to enhance the security and users’ ability to access shared bandwidth of an optical network. In this “pay-as-you-grow” supported system, the fiber impairment effects have been effectively reduced. The performance of the proposed system has been analyzed for variable input power (4–19 dBm) and transmission distance (10–70 km) supporting 120 active users under the influence of fiber nonlinearities, attenuation, dispersion and noise. Based on the numerical calculations, the proposed system using modified quadratic congruence (MQC) code is shown to provide better performance compared to multi diagonal, hadamard, zero cross-correlation (ZCC), shift ZCC and flexible cross-correlation codes. To validate the numerical analysis, the simulation of the proposed system at 160/40 Gbps data rate for 70 km downstream and greater than 70 km upstream fiber link transmission at 10−9 BER limit for 68 active users have been successfully demonstrated. Also, it has been shown that MQC code provides optimum results at 10 dBm input power over 55 km distance and supports more than 120 active users with high gain of − 1.97 dB and low noise figure of 2 dB. Further, the comparative performance of the proposed system with the previous latest works in literature reveals a superior performance of the system.

Design and analysis of a 32 × 5 Gbps passive optical network employing FSO based protection at the distribution level☆

A cost efficient and reliable single mode fiber and free space optics based hybrid 32×5Gbps ultra dense wavelength division multiplexed-passive optical network architecture employing optical comb and polarization multiplexing is proposed. The proposed architecture is a step forward towards shifting the next generation wireless network traffic over existing passive optical network to achieve the optimum bandwidth, capacity, quality of service and cost efficiency for mobile subscribers. Self-restorable passive optical networks having fiber based feeder and distribution paths are widely researched in various studies in the past. However, to the best of our knowledge, a self-restorable passive optical network architecture employing free space optics based protection path has not been proposed so-far. The effect of varying polarization mode dispersion from 0.02 to 0.06ps.km-0.5 and the refractive index structure parameter of the Gamma-Gamma channel model from 5×10-16 to 5×10-12m-2/3 is evaluated. A techno-economic performance analysis of the architecture for downstream is performed by considering both the distribution and protection paths. It has been shown that the receiver sensitivity for a polarization mode dispersion of 0.06ps.km-0.5 is around -22dBm and for strong turbulence is around -20dBm.

The performance comparison of hybrid WDM/TDM, TDM and WDM PONs with 128 ONUs

Abstract Here, we have simulated different unidirectional passive optical networks (PONs) technologies such as wavelength division multiplexing (WDM), time-division multiplexing (TDM) and hybridPONs with different users for varying fiber length, data rate, continuous wave laser power and number of users. Their performances based on the quality-factor (Q-factor) and bit error rate (BER) using OptiSystem software 7.0 with using an Erbium doped-fiber amplifier (EDFA) were compared. Our model used 16 and 128 users, where the performance of the unidirectional Hybrid WDM/TDM PONs with 4 wavelengths and 128 user systems have better high Q-factor and lower BER, compared to that of 128 user WDM PON and 128 user TDM PON systems.

A Bibliometric Analysis and Visualization of Passive Optical Network Research in the Last Decade

Passive optical networks (PONs) are the most successful broadband access solutions for its wide bandwidth, low-cost deployment worldwide, and maintenance. In the last decade, the diverse and prevalent research related to PONs sustains 330+ science citation index (SCI) articles per year, with 9.18 average citations per article, making it "big literature data". This article, for the first time, presents the graphical representation of knowledge base, knowledge domain, and knowledge evolution of PON research using co-citation analysis based on 3381 SCI publications worldwide from 2010 to 2019 in bibliometric visualization tool- CiteSpace. The bibliographic analysis focused on 528 important research articles, 34 hotspots, 155 research frontier keywords, 481 core authors, 185 cited authors, 58 countries, 254 institutions, and 118 journals. Based on the frequency of keywords, Modulation, WDM PON, Transmission, Semiconductor optical amplifier, and Dynamic bandwidth allocation are the dominant and turning points in the structural basis of PON research. The most prominent research hotspots appearing in recent years are Energy efficiency, NG-EPON, and Chaotic encryption. The trend of future research on PONs is from TWDM PON issues, fronthaul implementation in NG-PON2, 5G-PON and encryption methods for physical layer security. The leading core authors, institutes, countries, and journals were also identified related to the PON research. This analysis would serve as a comprehensive guide on the status and future research trends on PONs for the aspirant researchers.

Two 10 Gb/s directly modulated DBR lasers covering 20 nm wavelength range

We report the application of two widely tunable directly modulated distributed Bragg reflector (DBR) lasers to cover over 20 nm wavelength. 10 Gb/s data are transmitted up to 30 km distance at different wavelengths with the wavelength range. The results indicate that the DBR lasers are promising light sources for the next generation high capacity wavelength division multiplexed passive optical network (WDM-PON) systems.