Signal Remodulation Research Articles

5G wavelength-division-multiplexing-based bidirectional optical wireless communication system with signal remodulation employing cascaded reflective semiconductor optical amplifiers

Compared with previous generations, fifth-generation communications can provide faster download and upload speeds and support a greater number of connected devices. Integrating fifth-generation signals with optical wireless communication systems provides promising ways to afford higher transmission rates and faster wireless connectivity. Here we report a fifth-generation wavelength-division-multiplexing-based bidirectional optical wireless communication system with signal remodulation employing cascaded reflective semiconductor optical amplifiers to effectively remove the downstream data for uplink transmission. It shows a fifth-generation wavelength-division-multiplexing-based bidirectional optical wireless communication system using four wavelengths for communication. The uplink performance is substantially enhanced by using two reflective semiconductor optical amplifiers to remove the downstream data. The system achieves an aggregate transmission rate of 36.4 Gbit/s for both downlink and uplink transmissions over a 100-m optical wireless link. This demonstrated fifth-generation wavelength-division-multiplexing-based bidirectional optical wireless communication system employing cascaded reflective semiconductor optical amplifiers holds great potential for enhancing fifth-generation advanced communication capabilities.

An ultra-dense spacing-based PON by incorporating dual drive Mach–Zehnder modulator for comb generation

Abstract Wavelength division multiplexed passive optical is promising technique to achieve a high data rate and large number of user. The notable advantages of WDM PON is the combination of reliability, cheap in cost, accessible bandwidth, high security, large optical reach and it can support large number of ONU. There are multiple approaches to achieve high-speed WDN PON using different transmission techniques. In WDM, multiple lasers are required which increase the cost of the system. To reduce cost, an optical multicarrier generation system is proposed. An economical multiple carrier generation with the incorporation of sine generator and Mach–Zehndar modulator is demonstrated. Utmost work of sine generator and dual drive modulator was to attain low cost functioning of passive optical networks. Multicarrier generation was done and replacement of laser carriers with optical multicarrier generator. Carriers were generated with the frequency spacing of 20 GHz and these carriers were used in the passive optical networks with the tone-to-noise ratio of 40 dB, amplitude difference of 1.4 dB. For the transmission of downstream in the PON, differential phase shift keying was employed at 10 Gbps data speed. Transmission distance achieved was 30 km using single-mode fiber and this was a part of optical distribution network. Optical network unit was next part after ODN and signals were received with balanced receiver. Moreover, half signal was given to intensity modulator for the signal re-modulation. Bit error rate of 10–9 was achieved at all channels in the downstream. An upstream of 10 Gbps was accomplished in the passive optical network.

Tunable all-optical format conversion for BPSK to OOK based on highly nonlinear optical loop mirror

A scheme is proposed for tunable all-optical format conversion from BPSK to OOK signal without active phase locking under the highly nonlinear loop structure. The 20 Gbit/s BPSK is mapped to two-level amplitude signal by delay interferometer (DI). One carrier branch generated locally remodulates the amplitude information to phase based on cross-phase modulation (XPM) effect in the highly nonlinear fiber (HNLF). The other carrier propagates as a pump under symmetrical loop ensuring the stability of phase relationship. After interference and vector shifting in coupler, the wavelength-tunable OOK is obtained. Benefiting from the signal remodulation mechanism and symmetric loop setup, separate carrier extraction and additional phase-locking are not required. The feasibility of the scheme is demonstrated by constellation diagram, eye diagram and pattern transformation diagram in numerical simulations. At the BER of 10−3, the converted OOK has ∼0.7 dB and ∼1.9 dB optical signal-to-noise ratio (OSNR) improvement, respectively, compared to back-to-back (B2B) OOK under different quality of input signals. It is shown that the scheme optimizes the signal quality while converting signal formats. For low-quality BPSK with OSNR of 15 dB, the system indicates better noise tolerance. Furthermore, the scheme has potential scalability to bidirectional format conversion between BPSK and OOK.

Dedicated and broadcasting downstream transmission with energy-efficient and latency-aware ONU interconnection in WDM-PON for smart cities

Abstract Currently, Internet of Things (IoT) and use of Information & Communication Technology (ICT) have gained a lot of attraction for developing the smart cities. Wavelength division multiplexed passive optical networks (WDM-PON) are popularly used for supporting the high data rate IoT and ICT services. With the exponential growth of users and traffic demand in access networks, large energy consumption, OPEX, service reliability has become the most challenging bottleneck for smart cities. This paper proposes a flexible, wavelength division multiplexed passive optical network (WDM-PON) architecture which provides a dedicated point to point (P2P), broadcasting downstream transmission and latency-aware direct optical network units (ONUs) interconnection. Broadcasting downstream transmission is achieved by diverting a particular wavelength from the main path towards (N + 1) × (N + 1) star coupler (SC). Direct ONU interconnection is accomplished by separating the inter-ONU signal from the upstream path by using 50 GHz interleaver at the remote node (RN) and redirecting it towards ONUs. Direct ONU intercommunication avoids the complex re-routing, re-scheduling and re-modulation of the inter-ONU signal at optical line terminal (OLT) and thus increases the reliability and energy efficiency of the network. Broadcasting enables the best resource utilization, and direct ONU interconnection reduces the significant transmission latency among different communicating users. Proposed architecture reduces the operational cost and energy consumption of the network by reducing the processing by some components. By reducing the extra burden of the inter-ONU signal on downstream bandwidth, proposed architecture also provides the efficient bandwidth utilization.

20231 Gbit/s tricolor red/green/blue laser diode based bidirectional signal remodulation visible-light communication system

We propose and experimentally demonstrate a recorded 1-m bidirectional 20.231-Gbit/s tricolor R/G/B laser diode (LD) based visible-light communication (VLC) system supporting signal remodulation. In the signal remodulation system, an LD source is not needed at the client side. The client reuses the downstream signal sent from the central office (CO) and remodulates it to produce the upstream signal. As the LD sources are located at the CO, the laser wavelength and temperature managements at the cost-sensitive client side are not needed. This is the first demonstration, to our knowledge, of a >20 Gbit/s data rate tricolor R/G/B VLC signal transmission supporting upstream remodulation.

A Full-Duplex Radio-Over-Fiber Link Based on a Dual-Polarization Mach–Zehnder Modulator

A simple and low-cost full-duplex radio-over-fiber (RoF) link implementing wavelength reuse for short-range applications is proposed and demonstrated based on a dual-polarization Mach–Zehnder modulator (DPol-MZM). In the center unit, a continuous-wave optical carrier is sent to a DPol-MZM to generate an optical signal with data modulation along one polarization direction and an unmodulated optical carrier along the other orthogonal polarization direction. In the remote antenna unit, a polarization beam splitter is used to separate the modulated signal for downstream service and the unmodulated optical carrier for upstream signal remodulation. A proof-of-concept experiment is carried out. Performance of the established full-duplex RoF link operated at 18 GHz is investigated. The measured bit error rate and the error vector magnitude confirm that the proposed architecture is a promising candidate for future high-speed and low-cost short-range applications.

English

A novel integration scheme from time-division-multiplex passive optical network (TDMPON) to wavelength-division-multiplex PON (WDM-PON) using differential Quadreture phase-shift keying (DQPSK) for the downstream signal and wavelength-shifted amplitude-shift keying (WS-ASK) for the upstream signal is illustrated. The migration scheme does not change the existing fiber infrastructure. An optical filter is preinstalled at the optical networking unit (ONU) to select the desirable downstream wavelength for the WDM-PON and simultaneously demodulate the downstream DQPSK signal. Signal remodulation is used to generate the upstream signal by reusing the downstream wavelength. In the ONU, by wavelength shifting the upstream optical spectrum with respect to the downstream optical spectrum, the Rayleigh backscattering (RB) interference beat noise affecting the upstream signal can be significantly mitigated. The optimum bandwidth for the downstream DQPSK demodulation is analyzed.

Analysis of OOK Upstream Signal Remodulation for Different Data Rates in WDM PON Network

Analysis of OOK Upstream Signal Remodulation for Different Data Rates in WDM PON Network

TWDM-PON With Signal Remodulation and Rayleigh Noise Circumvention for NG-PON2

We propose and demonstrate a 40-Gb/s (4 × 10 Gb/s) downstream and 10-Gb/s (4 × 2.5 Gb/s) upstream time-wavelength-division-multiplexed passive optical network (TWDM-PON) using signal remodulation. Here, a downstream differential-phase-shift-keying (DPSK) signal and an upstream remodulated carrier-suppressed single-sideband non-return-to-zero (CS-SSB-NRZ) signal are used, which are wavelength shifted to circumvent Rayleigh backscattering (RB). A silicon-based optical microring resonator (MRR) filter is preinstalled at the optical networking unit (ONU) to select the desired downstream wavelength and simultaneously demodulate the downstream DPSK signal, which is then detected by a monolithic-integrated germanium-on-silicon (Ge-Si) photodiode (PD). Using silicon-based devices could be cost effective for the cost-sensitive ONU. The future monolithic integration of a silicon filter, a silicon detector, and a silicon modulator in the ONU is also discussed. The characteristics of the preinstalled silicon-based MRR and the Ge-Si PD are discussed. Error-free transmission (bit-error rate (BER) <;10-9 ) is achieved in both downstream and remodulated upstream signals after propagating through 20 km of standard single-mode fiber (SMF).

Simple and spectrally-efficient design of high capacity hybrid WDM/TDM-PON with improved receiver sensitivity

A simple design of hybrid wavelength division multiplexed/ time division multiplexed passive optical network (WDM/ TDM-PON) is demonstrated for the high capacity next generation access (NGA) network, having advantages of both WDM and TDM based PON techniques. A 10 Gbit/s differential quadrature phase shift keying (DQPSK) data signal is used at optical line terminal (OLT) for downstream, whereas a 2.5 Gbit/s inverse return-to-zero (IRZ) data signal with high extinction ratio is used for upstream signal by intensity re-modulation of downstream signal, no additional laser is used at optical network unit (ONU). Simulation results verify that aggregated 100 Gbit/s downstream transmissions of 10 DQPSK channels and aggregated 25 Gbit/s upstream transmission of 10 IRZ channels, using spectrally-efficient 50 GHz channel spacing, can be successfully achieved over a distance of 20 km with less than 1 dB transmission power penalties and improved receiver sensitivity.

Using Downstream DPSK and Upstream Wavelength-Shifted ASK for Rayleigh Backscattering Mitigation in TDM-PON to WDM-PON Migration Scheme

A migration scheme from time-division-multiplex passive optical network (TDM-PON) to wavelength-division-multiplex PON (WDM-PON) using differential phase-shift keying (DPSK) for the downstream signal and wavelength-shifted amplitude-shift keying (WS-ASK) for the upstream signal is demonstrated. The migration scheme does not change the existing fiber infrastructure. An optical filter is preinstalled at the optical networking unit (ONU) to select the desirable downstream wavelength for the WDM-PON and simultaneously demodulate the downstream DPSK signal. Signal remodulation is used to generate the upstream signal by reusing the downstream wavelength. In the ONU, by wavelength shifting the upstream optical spectrum with respect to the downstream optical spectrum, the Rayleigh backscattering (RB) interference beat noise affecting the upstream signal can be significantly mitigated. The optimum bandwidth for the downstream DPSK demodulation is analyzed. The downstream and upstream transmission performances at different split ratios are also discussed.

A Cost-effective and Spectrally-efficient Design of Centralized Light Source WDM-PON using Aggregated 160 Gbit/s DQPSK Modulation forDownstream and Re-modulated IRZ for Upstream Transmission

We propose and demonstrate a cost-effective and spectrally-efficient design of centralized light source wavelength division multiplexed passive optical network (WDM-PON). A 10 Gbit/s differential quadrature phase shift keying (DQPSK) data signal is used at optical line terminal (OLT) in the central office (CO) for downstream without pulse carving, whereas a 2.5 Gbit/s inverse return-to-zero (IRZ) data signal is used for upstream signal by re-modulation of downstream signal, no additional laser is used at optical network unit (ONU). Simulation results show that aggregated transmission of 160 Gbit/s downstream of 16 DQPSK channels and aggregated 40Gbit/s upstream of 16 IRZ channels, using spectrally-efficient 50 GHz channel spacing, can be successfully achieved over a distance of 20 km with lower transmission power penalties and improved receiver sensitivity in both downstream as well as upstream transmission.

An AWG based colorless WDM-PON with RZ-DPSK modulated downstream and re-modulation of DL signal for OOK upstream

We proposed an arrayed waveguide granting (AWG) based 10 Gbps full duplex wavelength division multiplexing passive optical network (WDM-PON) utilizing a return-to-zero differential phase shift keying (RZDPSK) modulation technique for down-link direction and then re-modulation of the downlink (DL) signal for the uplink (UL) direction using intensity modulation technique (OOK) with a data rate of 10 Gbps per channel. A successful cost effective colorless WDM-PON full duplex transmission operation for a data rate of 10 Gbps per channel, with a channel spacing of 60 GHz over a distance of 25 km without any optical amplification and dispersion compensation is achieved within low power penalty.

A novel duplex WDM-PON with DPSK modulated downstream and re-modulation of the downlink signal for OOK upstream

We experimentally demonstrate and analyze a 10 Gbit/s full duplex wavelength division multiplexing passive optical network (WDM-PON) system. A non-return-to-zero differential phase shift keying (NRZ-DPSK) modulation technique is first utilized for downlink direction, and then the downlink signal is re-modulated for the uplink direction using intensity modulation technique of on-off keying (OOK) with a data rate of 10 Gbit/s per channel. An effective colorless WDM-PON full duplex transmission system is achieved for the data rate of 10 Gbit/s per channel with a channel spacing of 60 GHz over the distance of 25 km with low power penalty.

40 Gb/s on–off keying downstream and 10 Gb/s on–off keying remodulated upstream signals in long-reach access network with multivideo services

In this demonstration, we propose and investigate a long reach passive optical network (PON) using four wavelength-multiplexed sig- nals with both on-off keying modulations for 40 Gb/s downlink traffic in 100 km fiber transmission without dispersion compensation. In the ex- change node, we can use four channels with video services broadcasting to each optical network unit (ONU) for the uplink signal remodulation. Hence, four wavelength-multiplexed video signals also can be used to inject into the corresponding reflective semiconductor optical amplifiers in each ONU for uplink signal remodulation to achieve a 4 × 2.5 Gb/s data rate. In addition, under the 32 split ratio PON system, the power penalties of nearly 6.7 and 1 dB could be measured at the bit error rate of 10 − 9 for the downlink and uplink traffic, respectively. C 2011 Society of Photo-Optical

Signal Remodulation Ring WDM Passive Optical Network with Rayleigh Backscattering Interferometric Noise Mitigation

We propose and demonstrate a novel and simple signal remodulation ring-based wavelength division multiplexed passive optical network (WDM-PON) scheme with the capability to mitigate the Rayleigh backscattering (RB) beat noise in colorless signal remodulation operation. The effects of RB can be avoided since the backscattering effects and upstream signals travel in opposite directions. Here, 10 Gb/s DPSK downstream is used to launch into reflective optical semiconductor amplifier (RSOA)-based optical network unit (ONU) for signal remodulation at 1.25 or 2.5 Gb/s on-off keying (OOK). Moreover, the network performance has also been analyzed and discussed.

Cooperative Transmission with Constant Envelope Modulations and Phase-Only Forward Relays

We propose the concept of Phase-Only Forward (PF) relays for cooperative communication involving constant envelope modulations. The technique enables the relaying nodes to maintain constant envelope signaling without the need to perform decoding and signal re-modulation. The bit-error-probability (BEP) of this PF technique, in conjunction with constant envelope CPFSK modulation in a time-selective Rayleigh fading environment and discriminator detection, was analyzed. Both cases of with and without antenna selection at the relay were considered. In the former case, a clever phase-adjustment scheme that allows the relay to maintain phase continuity was proposed. Our results indicate that without antenna selection, PF has a lower BEP than decode-and-forward (DF). It also delivers the same performance as amplify-and-forward (AF) when fading is quasi-static. In a time-selective fading environment, PF is not as efficient as AF without antenna selection. However with dual-antenna selection at the relay, PF has practically the same performance as AF even in a time-selective fading environment. We thus believe that PF is a cost-effective alternative to AF and DF, since signal re-modulation and expensive linear amplifiers are no longer needed at the relay to support non-constant envelope transmission. Finally, this phase-forward concept can be generalized to other continuous-phase modulation schemes as well as to PSK.

40-Gb/s downstream DPSK and 40-Gb/s upstream OOK signal remodulation PON using reduced modulation index

As different high speed signal-remodulation wavelength division multiplexed--passive optical network (WDM-PON) solutions up to 10 Gb/s have been proposed, researchers are going to further increase the data rate of PON towards 40 Gb/s or higher. However, scaling up from 10 Gb/s/wavelength to 40 Gb/s/wavelength PON is very challenging. Although many studies have been performed on upgrading the exiting 10 Gb/s network to 40 Gb/s, the study of the 40 Gb/s signal-remodulation network is very little. In this work, we will first study the chromatic dispersion effect on the signal-remodulation PON. Then, we will propose and demonstrate a signal-remodulation PON using 40-Gb/s downstream differential-phase shift keying (DPSK) and 40-Gb/s upstream on-off keying (OOK) signals. By using the reduced modulation index (RMI) of the downstream DPSK signal, the tolerance to the residual chromatic dispersion of the whole system can be greatly enhanced. Due to the reduced impact of the accumulated chromatic dispersion, the quality of the upstream remodulated OOK signal can be significantly improved. Besides, by detecting the downstream demodulated DPSK signal at the destructive output port of the demodulator, good quality of the demodulated DPSK signal can still be achieved.

A Bidirectional WDM Transport System Based on RSOAs and Optoelectronic Feedback Technique

Abstract-A bidirectional wavelength-division-multiplexing (WDM) transport system base on two reflective semiconductor optical amplifiers (RSOAs) and optoelectronic feedback technique is proposed and experimentally demonstrated. One RSOA is employed as a broadband light source and another RSOA in combination with optoelectronic feedback technique is used as wavelengths reuse and data signal remodulation scheme. System architecture is further simplified by using only one RSOA at the optical node, and system performance is further improved by optoelectronic feedback technique. Impressive performances of bit error rate (BER) (<;10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> ) were achieved for both 2.5 Gbps down-link and 1.25 Gbps up-link transmissions.

WDM PON using 10-Gb/s DPSK downstream and re-modulated 10-Gb/s OOK upstream based on SOA

A signal remodulation scheme of 10-Gb/s differential phase-shift keying (DPSK) downstream and 10-Gb/s on-off keying (OOK) upstream using a semiconductor optical amplifier (SOA) and a Mach-Zehnder intensity modulator (MZ-IM) at the optical networking unit (ONU) side for wavelength division multiplexed passive optical network (WDM PON) is proposed. Simulation results indicate that error-free operation can be achieved in a 20-km transmission, and the receiver sensitivity of return-to-zero differential phase-shift keying (RZ-DPSK) is higher than nonreturn-to-zero differential phase-shift keying (NRZ-DPSK) in the proposed scheme.