Ultra Wideband Signals and Systems in Communication Engineering

This paper reports the integration and experimental performance analysis of a GFDM-based 5G transceiver in a gigabit passive optical network (GPON), using radio over fiber technology. The proposed architecture enables to simultaneously transport two 5G candidates RF signals through an active GPON under real channel conditions. One signal is generated by a GFDM-based 5G prototype transceiver at 735 MHz, whereas the second one is synthetized by a vector signal generator at 26 GHz. A dual-drive Mach–Zehnder modulator has been utilized in the optical line terminal to modulate both signals, with the purpose of mitigating the interference between them. Particularly for the GFDM-based 735 MHz signal, a modulation error ratio (MER) of 40 dB has been obtained at RF-driven signal up to –9 dBm. Furthermore, the use of a digital predistortion scheme has been efficiently employed to reduce the impact of the nonlinear distortions and enhance MER. The 26-GHz RF signal, aimed for the 5G millimeter wave band, has been investigated as a function of error vector magnitude (EVM) for bitrates up to 1 Gbit/s. ${\text{EVM}}_{{\text{RMS}}}$ of 2.18% and 5.70% have been obtained for 100 Mbit/s and 1 Gbit/s, respectively. Finally, the latency and throughput measurements of the baseband signal originally running over GPON have shown no significant penalties.

Integration of a GFDM-Based 5G Transceiver in a GPON Using Radio Over Fiber Technology

We demonstrate 12-channel WDM-PON with 50 GHz channel spacing based on wavelength locked Fabry-Perot laser diodes. We also propose a few methods for the wavelength independent operation of an optical network termination. The wavelength division multiplexing passive optical network (WDM-PON) has been considered as an ultimate broadband access network due to its large guaranteed bandwidth, high security, easy upgradeability, bit rate and protocol transparencies. However, it requires expensive wavelength specified light sources and wavelength management of the optical transmitters in the subscribers’ side. Recently, a wavelength locked Fabry-Perot laser diode (F-P LD) to an injected spectrum-spliced amplified spontaneous emission (ASE) light was proposed for a low cost WDM source [1]. The injected ASE light forces the F-P LD to operate in a quasi single mode and suppresses the mode partition noise [2]. Therefore, we can use the wavelength locked F-P LD as a WDM source. In this paper, we demonstrate 12-ch WDM-PON with 50 GHz channel spacing using the wavelength locked FP LDs. The proposed WDM-PON can accommodate 80 channels. We also propose a few methods for the wavelength independent operation of an optical network termination (ONT) that is essential for a field deployable WDM-PON. The experimental setup to demonstrate 50 GHz channel spaced WDM-PON is shown in Fig. 1. The broadband light source (BLS) is the ASE light generated by a pumped Erbium-doped fiber. Two BLSs at different bands (C-band and L-band) are located at the central office (CO) for injection of broadband light into lasers located at the CO and the ONTs. The coarse wavelength division multiplexer (CWDM) filters are used to separate the different band signals. The arrayed waveguide gratings (AWGs) with Gaussian pass band are used at the CO and at the remote node (RN). The channel spacing and 3dB bandwidth of the AWG are 50 GHz and 22 GHz, respectively. To use a single AWG for both transmission bands (multiplexing of a band and demultiplexing of the other band or vice versa), we take advantage of periodic property of the AWG. We may need an athermal AWG for operation over wide temperature range. However, we used a conventional AWG for experimental purpose. The transmitter (Tx) includes a TO-can packaged F-P LD. Typical mode spacing and the front facet reflectivity of the F-P LD are 0.6 nm and 1 %, respectively. We use a heater to reduce the wavelength variation of the F-P LD induced by the ambient temperature variation. The wavelength variation of the laser with the heater is about 0.05nm/10°C when system operating ambient temperature is below the heater setting temperature of 55°C. We use conventional C-band (1548.9 nm ~ 1553.3 nm) for the upstream data transmissions and L-band (1581.3 nm ~ 1585.8 nm) for the downstream data transmissions. The F-P LDs are directly modulated at 155 Mb/s with a 2-1 pseudo random bit sequence (PRBS) pattern. The feeder fiber length between the CO and the RN is 20 km. The broadband light from C-band BLS was coupled into the transmission fiber and sent to the AWG2. Then, it was spectrally sliced by the AWG2 and injected into a F-P LD located at an ONT of each subscriber premises. The injection power into the F-P LD was -14 dBm/0.2 nm at peak. The upstream wavelength of each subscriber is determined by the wavelength of the injected spectrum sliced BLS, since a mode of F-P LD that is the nearest to the peak wavelength of the injected BLS is locked to the wavelength of the injected BLS. The upstream signals were multiplexed by the AWG2. The multiplexed signals were transmitted through the transmission fiber. At the CO, the received signals were demultiplexed by the AWG1. Then, the receiver recovered the upstream data. For the downstream data transmission, L-band BLS output was coupled into the AWG1. It was spectrally sliced and injected into the F-P LDs located at the CO. The rest processes are similar to the upstream signal. The measured upstream and downstream spectra are shown in Fig. 2. The upstream signal (a) and downstream signal (b) were measured at the input of the AWG1 and AWG2 with a tap coupler, respectively. Each spectrum shows multiplexed 12-ch signals and the BLS output. It may be noted that we do not try to match the output power of each channel. We measured the bit error rate (BER) for a single individual channel transmission and for 12-ch WDM Fig. 1. Experimental setup of 12-ch WDM-PON C Cclic A W G 2 L C yclic A W G 1 Central Office

Demonstration of Dense WDM-PON based on Wavelength locked Fabry-Perot Laser Diodes

A high spectral efficiency coherent microwave photonic link (MPL) supporting amplitude and phase modulation incorporating a digital phase noise cancellation is proposed and experimentally demonstrated. At the transmitter, a continuous-wave light wave is amplitude- and phase-modulated by two microwave vector signals carried by a microwave carrier at an identical frequency. The modulated optical signal is polarization multiplexed with an unmodulated optical carrier and transmitted over a length of a single-mode fiber (SMF). At the receiver, the optical signal is detected coherently by a coherent receiver to which a local oscillator (LO) laser source is also applied. Through advanced digital signal processing, the microwave vector signals are recovered, and the phase noise introduced by both the transmitter laser source and LO laser source is cancelled. An experiment is performed. The transmission of a 2.5-Gb/s 16-QAM and a 1.25-Gb/s QPSK microwave vector signals both at 2.5 GHz over a 25-km SMF is implemented. The total bit rate of the MPL is 3.75 Gb/s. The transmission performance of the MPL in terms of error vector magnitudes and bit error rates is evaluated.

A High Spectral Efficiency Coherent Microwave Photonic Link Employing Both Amplitude and Phase Modulation With Digital Phase Noise Cancellation

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.

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

An intensity-modulation and coherent-detection (IM/CD) microwave photonic (MWP) link with digital signal processing (DSP)-based phase noise cancellation is proposed and experimentally demonstrated. At the transmitter, the optical carrier is intensity-modulated by a radio-frequency (RF) signal and sent to a coherent receiver over a single-mode fiber (SMF). At the receiver, the intensity-modulated optical signal is coherently detected using a local oscillator (LO) laser source. The phase noise introduced by both the transmitter laser source and the LO laser source is converted into an amplitude noise at the output of the coherent receiver, which would be added to the in-phase component and quadrature component from the coherent receiver. The noise can be completely cancelled by summing the squared magnitudes of the in-phase and quadrature components from the coherent receiver, which can be implemented using a DSP unit. Error-free transmission of a 1.25-Gb/s quadrature phase shift keying modulated RF signal with a center frequency of 1.6 GHz over 25-km SMF is experimentally demonstrated. For a signal with a bit rate of 834 Mb/s, the receiver sensitivity can reach ${-}{\rm 24.5}~{\rm dBm}$ which is 20 dB better than that based on an intensity-modulation and direct-detection MWP link.

Digital Phase Noise Cancellation for a Coherent-Detection Microwave Photonic Link

A broadband millimeter-wave (mmW) at 60-GHz band and an impulse radio ultra-wideband (IR-UWB) over a colorless 100-GHz dense wavelength division multiplexing (DWDM) passive optical network (PON) that supports simultaneous transmission of a broadband mmW signal, a UWB signal and a wireline baseband signal is experimentally demonstrated. At the transmitter, a polarization modulator (PolM) is employed, which operates in conjunction with a polarization controller (PC) and a polarization beam splitter (PBS) as an equivalent Mach-Zehnder modulator (MZM). For 60-GHz and IR-UWB signal transmission, the equivalent MZM is biased at the minimum transmission point to generate two sidebands that are separated at a frequency in the 60-GHz band, and the wireless signals (60 GHz and IR-UWB) are carried by the two sidebands. For the wireline baseband transmission, the equivalent MZM is biased at the maximum transmission point to generate only the optical carrier, and the wireline signal is carried by the optical carrier. The wireline signal and the wireless signals are orthogonally polarized and sent over a single-mode fiber (SMF) to a base station (BS). For each WDM channel in the central station (CS) and the BS, since no optical filters are employed, colorless operation is supported. Point-to-point error-free transmission of a 1.25-Gbps mmW signal, a 1.25-Gbps IR-UWB signal and a 10-Gbps wireline signal over a 25-km SMF is experimentally demonstrated. The number of users that can be supported by the proposed colorless WDM-PON is estimated based on the measured receiver sensitivities.

Millimeter-Wave and UWB Over a Colorless WDM-PON Based on Polarization Multiplexing Using a Polarization Modulator

Wavelength reuse in a symmetric ultra-wideband (UWB) over wavelength-division-multiplexing passive optical network based on injection locking of a Fabry-Perot laser diode (FP-LD) and polarization multiplexing is proposed and experimentally demonstrated. In the proposed scheme, the downstream UWB signal and baseband signal are generated and polarization multiplexed in the central station and sent to a base station (BS) over an optical fiber. At the BS, one of the downstream signals is selected to injection lock the FP-LD. It is demonstrated theoretically and experimentally that the upstream service performance is less sensitive to the modulation depth of the downstream UWB signal than the baseband signal, and the use of the downstream UWB signal as the injection signal would contribute to a better transmission performance for both the downstream and upstream services. Thus, the downstream UWB signal is selected as the injection signal. An experiment is performed. When the FP-LD is injection locked by a downstream UWB signal, a clear optical carrier is generated which is reused for upstream UWB and baseband transmission. A bidirectional point-to-point transmission of 1.25 Gb/s UWB signal and 10 Gb/s baseband signal over 25-km single-mode fiber using a single wavelength is demonstrated. The bit error rate performances and the eye diagrams for both downstream and upstream transmissions are measured.

Wavelength Reuse in a UWB Over WDM-PON Based on Injection Locking of a Fabry–Pérot Laser Diode and Polarization Multiplexing

Wavelength reuse in a bidirectional UWB over fiber system using a polarization modulator (PolM) and an electro-absorption modulator (EAM) is proposed and experimentally demonstrated. Since the PolM functions as a special phase modulator that supports phase modulation along the two principal axes with opposite modulation indices and the EAM is a polarization-independent component, the signals due to the phase-modulation to intensity-modulation (PM-IM) conversion along the two orthogonal directions in the upstream link will be complementary and cancelled out, thus the impact of the downstream signal to the upstream transmission due to the PM-IM conversion is fully eliminated. Error-free bidirectional transmission of a 1.25-Gbps UWB signal over 17 km single-mode fiber (SMF) is demonstrated. A power penalty due to the wavelength reuse for upstream transmission is measured to be as low as 0.2 dB.

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Wavelength reuse in a bidirectional UWB over fiber system.

A novel wavelength reuse scheme based on phase-modulation to intensity-modulation (PM-IM) conversion and destructive interferencing using a polarization modulator (PolM) and a fiber Bragg grating (FBG) in an ultra-wideband (UWB) over fiber (UWBoF) system is proposed and experimentally demonstrated In the proposed scheme, a PolM and an FBG in the central station (CS) are used to generate intensity-modulated impulse UWB signal based on PM-IM conversion The downstream UWB signal is sent to a base station (BS) over an optical fiber At the BS, when the principle axis of the polarizer is aligned with one of the two orthogonal states of polarization (SOPs), the downstream UWB signal is received and detected When the principle axis of the polarizer is oriented at a special angle to one of the two orthogonal SOPs, a clear optical carrier without intensity modulation is generated, which is then reused for upstream UWB data transmission A theoretical analysis is performed which is verified by an experiment A bidirectional point-to-point transmission of 125 Gb/s UWB signal over 25-km single-mode fiber (SMF) using a single light source from the CS is demonstrated The receiver sensitivity and the BER performance for both downstream and upstream transmissions are measured

Tong Shao

Papers

Digital Phase Noise Cancellation for a Coherent-Detection Microwave Photonic Link

Millimeter-Wave and UWB Over a Colorless WDM-PON Based on Polarization Multiplexing Using a Polarization Modulator

Wavelength Reuse in a UWB Over WDM-PON Based on Injection Locking of a Fabry–Pérot Laser Diode and Polarization Multiplexing

Wavelength reuse in a bidirectional UWB over fiber system.

Wavelength Reuse in a UWB Over Fiber System Based on Phase-Modulation to Intensity-Modulation Conversion and Destructive Interferencing