Advanced design for lightweight structures: Review and prospects

Using orthogonal-frequency-division-multiplexing (OFDM) format for passive optical network (PON) is a subject of great interest for recent research works. OFDM signal has high spectral efficiency, high tolerance to the fiber chromatic dispersion and the high flexibility on both multiple services provisioning and dynamic bandwidth allocation. In this paper we study the use of OFDM signals for optical access networks, including carrier distributed PON, heterogeneous optical wired/wireless network and a 100 Gb/s OFDM-PON. We first quantify the performance of the OFDM signal when subjected to the noise produced by two different Rayleigh backscattering (RB) components that are present in the carrier-distributed PON. Then, based on these results, we also study the possibility of using OFDM for signal remodulation in a long-reach (LR)-PON. We propose carrier-distributed OFDM PONs using a dual-feeder fiber architecture and wavelength-shifting to mitigate the RB noise. Afterwards, we propose heterogeneous optical wired/wireless access networks, combining 10 Gb/s PON and 10 Gb/s OFDM radio-over-fiber (ROF) network. Finally, we propose a 100 Gb/s OFDM-PON using subcarrier multiplexing (SCM).

/pdf/studies-of-ofdm-signal-for-broadband-optical-access-networks-1ftfed09n5.pdf

Studies of OFDM signal for broadband optical access networks

The passive optical network (PON) using orthogonal frequency-division multiplexing (OFDM) is a subject of many research works recently. The OFDM signal is especially good for long reach (LR)-PON due to its high tolerance to chromatic dispersion and high spectral efficiency. We study, for the first time, the possibility of using OFDM for signal remodulation in LR-PONs. Three different colorless optical networking unit (ONU) architectures, electroabsorption modulator-based, reflective semiconductor optical amplifier-based and injection-locked Fabry-Perot laser diode-based ONUs, are tested and compared. Error-free operations are achieved in 100-km fiber transmission without dispersion compensation.

/pdf/signal-remodulation-of-ofdm-qam-for-long-reach-carrier-3cos0kl62k.pdf

Signal Remodulation of OFDM-QAM for Long Reach Carrier Distributed Passive Optical Networks

We propose a method to locate precisely faults in wavelength-division-multiplexing (WDM) passive optical network (PON) by using a wavelength tunable chaotic laser The chaotic laser consists of a multiple-longitudinal-mode Fabry-Perot (FP) laser diode whose modes match the channels of WDM-PON, and an optical feedback loop including a filter The loop feeds a proportion of light of one mode that passes through the filter back into laser cavity to generate chaotic light By adjusting the filter frequency, we can tune the wavelength of the chaotic light, and diagnose the corresponding branch of WDM-PON We demonstrate a proof-of-concept experiment for detection of three ITU channels Fault location is realized by correlating the back-reflected light with its time-delayed duplicate The results show that spatial resolution of 2 cm and dynamic range of about 208dB can be achieved In addition, we have experimentally studied the effects of the strength level and wavelength mismatching of the feedback light on the chaotic output of the FP laser

Precise Fault Location in WDM-PON by Utilizing Wavelength Tunable Chaotic Laser

The transmission performance of multichannel adaptively modulated optical orthogonal frequency-division multiplexing (AMOOFDM) signals is investigated numerically, for the first time, in optical-amplification-free and chromatic-dispersion-compensation-free intensity-modulation and direct-detection systems directly incorporating modulated distributed feedback (DFB) lasers (DMLs). It is shown that AMOOFDM not only significantly reduces the nonlinear wavelength-division multiplexing (WDM) impairments induced by the effects of cross-phase modulation and four-wave mixing but also effectively compensates for the DML-induced frequency chirp effect. In comparison with conventional modulated optical orthogonal frequency-division multiplexing (OFDM), which uses an identical signal modulation format across all the subcarriers, AMOOFDM improves the maximum achievable signal transmission capacity of a central WDM channel by a factor of 1.3 and 3.6 for 40- and 80-km standard single-mode fibers, respectively, with the corresponding dynamic input optical power ranges being extended by approximately 5 dB. In addition, AMOOFDM also causes the occurrence of cross-channel complementary modulation format mapping among various WDM channels, leading to considerably improved transmission capacities for all individual WDM channels.

Adaptive-Modulation-Enabled WDM Impairment Reduction in Multichannel Optical OFDM Transmission Systems for Next-Generation PONs

In order to reduce the cost for delivering future broadband services, network operators are inclined to simplify the network architectures by integrating the metro and access networks into a single system. Hence, extended reach passive optical networks (ER-PONs) have been proposed. ER-PON usually has four new features: high data rate in both upstream and downstream signals (>1 Gb/s); reach extension to >100 km; a high split ratio (>100); and using wavelength division multiplexing (WDM). In this work, we propose and demonstrate a highly spectral efficient ER-PON using 4 Gb/s OFDM-QAM for both upstream and downstream signals, while achieving a high split-ratio of 256. The ER-PON employs optical components optimized for GPON (bandwidth of ∼1GHz) and reaches 100 km without dispersion compensation. Numerical analysis using 16, 64 and 256-QAM OFDM are also performed to study the back-to-back receiver sensitivities and power penalties at different electrical driving ratios.

https://ir.nctu.edu.tw:443/bitstream/11536/8480/1/000258368600048.pdf

WDM extended reach passive optical networks using OFDM-QAM

https://ir.nctu.edu.tw:443/bitstream/11536/6164/1/000274479000006.pdf

Utilization of self-injection Fabry–Perot laser diode for long-reach WDM-PON

We propose and experimentally demonstrate a continuous wave (CW) tunable-wavelength fiber laser using self-seeding Fabry-Perot laser diode (FP-LD) without optical amplifier inside gain cavity. By employing a tunable bandpass filter (TBF) and a fiber reflected mirror (FRM) within a gain cavity, the fiber laser can lase a single-longitudinal wavelength due to the self-seeding operation. The proposed tunable wavelength laser has a good performance of the output power (> -15 dBm) and optical side-mode suppression ratio (> 40 dB) in the wavelength tuning range of 1533.75 to 1560.95 nm. In addition, the output stabilities of the fiber laser are also investigated.

https://ir.nctu.edu.tw:443/bitstream/11536/9775/1/000252234800050.pdf

Cost-effective wavelength-tunable fiber laser using self-seeding Fabry-Perot laser diode

https://ir.nctu.edu.tw:443/bitstream/11536/6892/1/000274478700003.pdf

Multiwavelength erbium-doped fiber ring laser employing Fabry-Perot etalon inside cavity operating in room temperature

In this investigation, we propose and experimentally investigate a simple self-restored fiber Bragg grating (FBG)-based sensor ring system. This proposed multi-ring passive sensing architecture does not require active components in the network. In this experiment, the network survivability and capacity for the multi-point sensor systems are also enhanced. Besides, the tunable laser source (TLS) is adopted in a central office (CO) for FBG sensing. The survivability of an eight-point FBG sensor is examined and analyzed. It is cost effective since the sensing system is entirely centralized in the CO. Experimental results show that the proposed system can enhance the reliability of the FBG sensing network for large-scale and multi-point architecture.

https://iopscience.iop.org/article/10.1088/0957-0233/20/4/043001/pdf

Fu Yuan Shih

Papers

WDM extended reach passive optical networks using OFDM-QAM

Utilization of self-injection Fabry–Perot laser diode for long-reach WDM-PON

Cost-effective wavelength-tunable fiber laser using self-seeding Fabry-Perot laser diode

Multiwavelength erbium-doped fiber ring laser employing Fabry-Perot etalon inside cavity operating in room temperature

A simple self-restored fiber Bragg grating (FBG)-based passive sensing ring network