We studied the influence of frequency and phase noise of semiconductor laser on the performance of photonics assisted terahertz wave system. The laser spectrum is Lorentzian intrinsic shape when only Gaussian white noise exists. The phase noise of the laser increases with the increase of the Lorentzian spectral linewidth of the laser. When considering 1 f noise, the laser frequency will be superimposed with 1 f noise. The 1 f noise in the low-frequency band will make the reconstructed laser spectrum of the whole frequency noise tend to be non-Lorentzian shape, which has a serious impact on system performance. When the system is affected by the resonance frequency, the side lobes appearing on both sides of the main peak of the laser spectrum also have a certain impact on the system performance. We simulated dual-polarization (DP) 16-ary quadrature amplitude modulation (16QAM) signal transmission up to 60Gbaud on a 50km standard single mode fiber (SSMF) at 300GHz.
To combine the merits of fiber communication and wireless communication, photonics-aided terahertz-wave (THz-wave) technology has become a popular technology in recent years. In this paper, a 92 Gbit/s photonics-aided 0.3-THz wireless transmission system based on digital sub-carrier multiplexing (DSCM) is proposed and simulated. In order to compensate the phase noise, both Viterbi-Viterbi and maximum likelihood (VV&ML) algorithm and decision directed digital phase lock loop (DD-PLL) method are considered and compared. According to the simulation results, DSCM based scheme can provide better performance than single carrier (SC) based scheme in the case of low received optical power (ROP) or input optical power (IOP) while there is no advantage in the case of high ROP or IOP. For SC based scheme, DD-PLL has 1 dB sensitivity gain compared with VV&ML when BER drops from 10-3 to 10-4, while 2 dB sensitivity gain was obtained for DSCM based scheme for ROP. For SCM based scheme, DD-PLL has 1 dB sensitivity gain compared with VV&ML when BER drops from 10-3 to 10-4. On the whole, DD-PLL outperforms VV&ML in terms of performance in high ROP case for both SC and SCM based scheme. Besides, DD-PLL has lower computation complexity than VV&ML.
KEYWORDS: Digital signal processing, Data centers, Optical amplifiers, Transmitters, Signal detection, Modulation, Signal processing, Picosecond phenomena, Modulators, Forward error correction
Propelled by bandwidth-hungry cloud services, the ongoing growth of intra-datacenter traffic drives the development of high-speed short-reach transceivers, which calls for next generation optical interfaces of 800-GE or even 1.6-TbE. Conventional intensity-modulation direct-detection (IM/DD) systems still dominate the market for high speed short reach optical interconnects due to its simplicity and low cost compared with coherent solutions. Several advanced techniques to achieving net data rates around 200∼250 Gbps have been demonstrated. Effective digital signal processing (DSP) for signal recovery are always used in these systems, including digital pre-distortion, digital timing recovery, feed-forward and decision feedback equalization (FFE/DFE) and stronger forward error correction. Probabilistic shaping (PS) has been introduced for 200G+ per lane IM/DD systems. Semiconductor optical amplifier (SOA) and PS can be potentially used for 200G+ per lane IM/DD systems at O-band over 10 km SMF. There are two main transmission impairments: the nonlinear impairments from the nonlinear region of the electro-optical components, and linear impairments from the bandwidth constraint of the optoelectronic devices and chromatic dispersion. Single-lane 200G+ transmission is difficult to realize due to the nonlinear impairments and the strong bandwidth constraint of optoelectronic devices. In recent years, we have experimentally demonstrated several 200G+ per lane IM/DD short-reach transmission system, making it a promising scheme for data center short-reach applications.
KEYWORDS: Video, Extremely high frequency, Video compression, Ka band, Phased array optics, Sensors, Data transmission, Cameras, Antennas, Heterodyning
With the large-scale commercialization of 5G and the continuous evolution of the ultra-high-definition video industry, the next five years will be a period of strategic opportunities for the technological development and achievement transformation of the ultra-high-definition video industry. 5G mm-wave such as 28GHz in Ka-band will drive the rapid development of ultra-high-definition video industry applications. In this paper, we experimentally demonstrate a real-time full-duplex photonic-assisted 28GHz mm-wave communication system for video services. The experimental results show that our system supports real-time data error-free transmission of 1.25Gbaud and bit error rate level of 10-12 at 2.125 Gbaud under the case of 5km fiber and 1.6m wireless distances. Additionally, we also demonstrate the real-time full-duplex transmission of 1080p uncompressed video with the overall bandwidth of 1.485Gbps. It means this system can enable at least 8 channels of 8K video or 20 channels of 4K video to be live and on-demand at the same time after using video compression techniques. According to the above results, we believe that this system can promote the development of 5G mm-wave real-time ultra-high-definition video services for indoor or outdoor scenarios.
In this paper, 28GHz millimeter wave (MMW) in n257 band which is one of the recommended frequency bands for beyond 5G, has been demonstrated by experiment for optical wireless access. The MMW antenna with the bandwidth of 26.5 ~ 29.5GHz and an envelope detector with a 3dB bandwidth of about 500MHz are used to enable 4-ary pulse amplitude modulation (PAM4) signal transmission over 5km fiber and 1.6m wireless distances in our experiment. In order to compensate the linear and nonlinear impairments of the optical wireless links, the long short-term memory (LSTM) neural network nonlinear equalizer is adopted in the receiver DSP. Additionally, the traditional linear equalizer (LE) and Volterra equalizer (VE) are also conducted for comparison. The results show that neither the performances of LE nor VE can reach the 7% hard-decision forward error correction (HD-FEC) threshold (3.8×10-3) in the case of 5 Gbaud PAM4 transmission over 5km fiber and 1.6m wireless distances. Instead, after adopting the LSTM equalizer, the bit error rate can be reduced to approximate 1×10-3, which reveals a noticeable performance improvement. Moreover, the performances of the three kinds of equalizers at different transmission rates are further studied. We find that the LSTM can help improve the system capacity from below 9Gbps to above 10Gbps at 7% HD-FEC threshold, which means more than 10 percent improvement has been achieved. According to the above results, we believe that the LSTM equalizer will facilitate the large-capacity communication for the upcoming 5G MMW in fiber wireless access networks.
Wireless communication and sensing show more and more similarities in system design and signal processing flows. A common transmitter sharing is preferred for communication and sensing to reduce equipment cost, hardware size, and power consumption. In this paper, we propose and demonstrate a joint photonic transmitter for wireless communication and sensing at mmW-band based on heterodyne detection. The key device of the photonic transmitter is a dual-drive Mach- Zehnder modulator (DMZM) and a multichannel tunable optical filter (MTOF). The two arms of the DMZM are driven by a specially coded sine wave and a specially coded single chirped linear frequency modulation (LFM) wave, respectively. Besides, both of the two amplitude-coded waves are simultaneously modulated onto the two lasers coupled into the DMZM. By filtering out appropriate sidebands using the MTOF, an amplitude-shift-keying (ASK) signal for wireless communication and a dual-chirp LFM for sensing at mmW-band can be simultaneously generated after heterodyne detection. When the product of the two baseband signals used to code the sine and LFM waves is fixed, the envelope of the mmW LFM wave for radar sensing keeps constant. The simulation results show that a 11.5-Gbit/s ASK signal and a dual-chirp LFM signal with constant envelope are successfully generated at the same time. By properly setting the frequencies of the lasers and the sine wave, the generated ASK signal can be centered at 28GHz for 5G mmW communication, and the generated LFM wave can be distributed around 79GHz for vehicle radar sensing. Thanks to the dual chirps of the mmW LFM wave, range-Doppler decoupling is achieved.
Network function virtualization (NFV) is a promising technology that has attracted much attention in both academia and industry. With IT resource virtualization, NFV paradigm could decouple network functions (NFs) from special-purpose hardware equipment, providing more flexibility to network service providers and facilitating a better sharing of physical infrastructure when implementing NFs. Meanwhile, with the introduction of flexible-grid elastic optical networks (EONs) and virtualized transponders (vTPs), a new concept of resource virtualized elastic optical networks (RvEON) is emerged in this context, which has not only realized link-tier spectrum virtualization in each fiber link, but also realized node-tier TP virtualization within each substrate node. In this paper, we for the first time study how to implement efficient virtual network function service chaining (VNF-SC) in inter-DC RvEONs, taking into account subcarrier and modulation resources of the vTPs equipped in network nodes, in addition to fiber-link spectrum and IT resources. First, an integer linear programming (ILP) model for the VNF-SC deployment problem is formulated for jointly allocating these multi-dimensional resources. Then, for scalability, we also propose a heuristic based on Maximum Reuse with Decentralization Principle (MR-DP). The main idea behind the heuristic is that deploying the VNFs in a much more load-balanced manner can facilitate to maximize reuse the most existing VNFs to save the IT resources. The simulation results indicate that the proposed MR-DP heuristic can allow the minimum number of the deployed VNFs, while consuming the similar amount of other resources, compared with other two benchmark schemes.
We proposed and demonstrated a centrally controlled and self-healing wavelength division multiplexing passive optical network with colorless optical network units (ONUs) based on optical carrier suppression technique. By switching the affected data in the OCS signal sideband to an alternate protection path, only one optical switch is provisioned at the optical line terminal, which is controlled by a logic control circuit upon monitoring of power outage on the working path. The proposed scheme can reliably protect against both distribution and feeder fiber failures. Moreover, gain-saturated reflective semiconductor optical amplifiers are used as colorless transmitters in ONUs. The protection scheme feasibility and system performances are experimentally verified with 10 Gb/s downstream and 1.25 Gb/s upstream data in both working and protection modes. The protection switching time was measured to be around 1 ms.
We present a novel upstream multiwavelength shared ethernet passive optical network architecture, based on a proposed self-seeding Fabry-Pérot laser diode (FP-LD) at the optical network unit. The performances of the wavelength and power stability, side-mode suppression ratio, and tuning range for the proposed tunable self-seeding laser module are experimentally investigated. The bit-error-rate measurement is performed with direct modulation on FP-LD of 1.25 Gbps upstream data. The performance benefits from the upstream wavelengths sharing are showed via simulations.
We propose a simple configuration of wavelength-tunable self-seeding Fabry-Perot fiber laser at ONUs for upstream
transmission in hybrid WDM/TDM PON. The performances of the side-mode suppression ratio (SMSR), tuning range,
wavelength and power stability for the proposed laser module are experimentally investigated. The performance benefits
from the upstream wavelengths sharing are showed via simulations.
The Hybrid WDM/TDM PON, which combines Wavelength-division multiplexing (WDM) with TDM technology, is
presented as a promising solution for the next generation of optical access network. To realize the statistical multiplexing
of upstream wavelength resources, some optical tunable components are introduced in the optical network unit (ONU).
However, switch latency (SL) of these components is an important parameter that will constrain the performance of
Hybrid WDM/TDM PON. In this paper, we for the first time demonstrate and analyze the effect of channel switch
latency (SL) based on the extended WDM IPACT scheme via simulations. The simulation results show that the
performance such as delay, packet lost ratio, queue length and utilization will be constrained by SL, and the
WDM-IPACT-SL can adaptively adjust the channel switch time according to the different SL so as to reduce the
degeneration of the network performance in the practical applications of. Hybrid WDM/TDM PON
A fiber sensor configuration suitable for simultaneous measurement of temperature and strain is investigated. The sensor
consists of a high-birefringence fiber loop mirror concatenating with an erbium-doped fiber. The high-birefringence fiber
used in the configuration is capsule shaped polarization maintaining fiber, which serves as the sensor element. While the
erbium-doped fiber acts as the temperature compensation module. By monitoring the peak power variation and peak
wavelength shift, it is feasible to simultaneously measure temperature and strain. The experimental results show that the
mean square errors for temperature and stain are 0.35°C and 13.34με, respectively. The proposed sensor configuration
shows several merits, including simple in structure, easy fabrication, low cost and high sensitivity.
Fault-tolerant scheduling is an important issue for optical gird applications because of a wide range of grid resource
failures. To improve the availability of the DAGs (directed acyclic graphs), a primary-backup approach is considered
when making DAG scheduling decision. Experiments demonstrate the effectiveness and the practicability of the
proposed scheme.
We propose a novel multicast-enable wavelength-division-multiplexed (WDM) passive-optical-network (PON)
architecture that uses two sidebands of Optical Carrier Suppressed (OCS)-DPSK signal to carry the unicast and multicast
data. The multicast wavelength control is realized through a Wavelength Selective Switch (WSS). At the optical line
terminal (OLT), for each WDM channel, a single drive Mach-Zehnder modulator (MZM) is used to generate a subcarrier
double-sideband (DSB) DPSK signal. Then, the lower-sideband signals are separated by an interleaver and subsequently
modulated to deliver the multicast data, while the remaining upper-sideband DPSK signals carry the downstream unicast
data. In the optical network units (ONUs), part of the downstream unicast signal power is re-modulated for upstream
transmission, which enables color-free ONUs. This proposed scheme is experimentally demonstrated with a 1.25Gb/s
downstream unicast and multicast data.
We propose a novel scheme to overlay multicast service over a wavelength-division-multiplexed (WDM) passive optical
network (PON) based on dynamic wavelength reflection scheme. At the optical line terminal (OLT), for each WDM
channel, a dynamic wavelength reflector is used to selectively bypass the corresponding optical carrier to avoid multicast
data superimposition, while the remaining optical carriers go through the dynamic wavelength reflector and
simultaneously carry the multicast data. The proposed scheme is experimentally demonstrated with 5-Gb/s downstream
unicast, multicast data and 625-Mb/s upstream re-modulated data.
We propose a novel scheme to realize unicast and multicast in WDM-PON. Unicast data and multicast data are
modulated in Amplitude Shift Keying (ASK) format and Differential Phase Shift Keying (DPSK) format respectively.
Reflective Semiconductor Optical Amplifier (RSOA) is used to selectively erase the DPSK signal by controlling the
optical switch, and multicast is realized.
This paper studies the problem of the implementation of distributed computing applications in local area networks. We
propose a novel Dynamical Wavelength Scheduled Wavelength Division Multiplexing Passive Optical Network (WDMPON)
architecture, in which the number of the available upstream wavelength channels is greatly less than that of optical
network units (ONU). And we experimentally demonstrate the feasibility of the proposed WDM-PON, which enables
dynamically scheduling upstream data in the time division multiplexing (TDM) and WDM scheme from ONU to
optical line terminal (OLT). The Time-Wavelength Co-Allocation (TWCA) Problem is defined in the proposed WDMPON
architecture to aggregate large files for distributed computing applications and three scheduling algorithms are
presented to solve this problem. The significant improvement compared with the conventional TDM-over-WDM PON is
illustrated through simulations.
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