Millimeter wave (mm-wave) and microwave frequency has become a hot research topic in recent years. Comparing to traditional wireless communication frequency, microwave possesses larger available bandwidth, which is up to tens of gigahertz, so that it can support advanced digital services with ultra-high bit rate. To support the transmission rate over 100Gbit/s in an optical wireless system, forward error correction (FEC) is adopted in real-time communication systems to correct bit errors. Polar code is a kind of FEC which can theoretically achieve channel capacity as the code length tends to infinity. In this paper, we experimentally demonstrate a photonics-aided microwave communication system at K-band. With polar coding, 20-Gbit/s signal is transmitted over 20m wireless link. Our experimental results show that BER performance of such optical wireless system can be improved largely after we employ polar coding.
KEYWORDS: Laser sintering, Receivers, Modulation, Digital signal processing, Signal processing, Telecommunications, Data communications, Signal detection, Absorbance, Active optics
The intensity modulation and direct detection (IM/DD) systems have been widely investigated and demonstrated to fulfil the requirement of short reach data communication links with simple implementation. DMLs are a low cost solution for IM/DD systems due to their low power dissipation, small footprint and high output optical power. However, for DMLs, the driving current can influence the optical density at its active region, hence the intrinsic chirp affects the generated optical carrier and results in distortions of the signals, which reduces transmission rates and signals decision accuracy. We propose a machine learning-based decision technique to mitigate nonlinear distortions of the DMLs without using any nonlinear processing, and demonstrate a 60-Gb/s PAM-8 IM/DD system using a DML. About 0.6-dB receiver sensitivity improvement is achieved after 2km transmission.
We experimentally demonstrate a photonics-based radio-over-fiber orthogonal-frequency-division-multiplexing (ROFOFDM) system located within the terahertz-wave (THz-wave) frequency range from 350GHz to 510GHz. In our demonstrated system, 4.46-GHz-bandwidth OFDM quadrature-phases-shift-keying (OFDM-QPSK) THz-wave signal within the frequency range from 350GHz to 510GHz, can be generated and delivered over 2.5-inch wireless transmission distance, with a bit-error ratio (BER) under the hard-decision forward-error-correction (HD-FEC) threshold of 3.8×10-3. In our demonstrated system, 4.46-GHz-bandwidth OFDM-QPSK THz-wave signal at 450GHz is delivered over up to 35-km fiber transmission distance and 2.5-inch wireless transmission distance, with a BER of 3.8×10-3.
KEYWORDS: Signal generators, Digital signal processing, Eye, Receivers, Modulation, Signal detection, Multiplexers, Oscilloscopes, Modulators, Binary data
With the popularization of data center and other bandwidth hungry inter-connect applications, the desired capacity of short reach optical network has exponentially increased. In order to realize high-speed transmission, a few modulation formats or schemes, such as PAM4 and DMT are proposed and experimentally demonstrated. However, these modulation formats need expensive DAC and ADC as well as DSP procession. OOK modulation has simple architecture and high receiver sensitivity. Duo-binary signal is a special OOK signal. Here we experimentally demonstrate a record bit rate of 160-Gb/s OOK electrical signal generation, and realize a duobinary optical signal at a bit rate of 160Gb/s transmission and detection.
KEYWORDS: Orthogonal frequency division multiplexing, Modulation, Modulators, Digital signal processing, Signal processing, Quadrature amplitude modulation, Transmittance, Receivers, Single sideband modulation, Signal generators
To meet the increasing bandwidth demand for rapidly growing data flow from the wide spreading multimedia services, broadband Internet, and cloud services, 100G and even beyond data transmission based on compact and low-cost transceivers have been intensively studied in short-reach links, access, inter data-center-interconnections, metro and regional networks. For these systems, direct-detection is more attractive due to the lower system cost and power consumption. In this paper, we review four advanced modulation formats including pulse amplitude modulation-4 (PAM-4), carrier-less amplitude and phase modulation-16 QAM (CAP-16), discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S OFDM) and Duobinary with low-cost direct detection in 100 Gb/s/λ short-reach and metro optical transmission systems. These modulation formats are all experimentally demonstrated with similar digital signal processing algorithms. Three kinds of chromatic dispersion (CD) compensation ways named pre-CD method, single sideband (SSB) and dispersion compensating fiber (DCF) are also compared. Two types of modulators including IQ modulator and dual-drive Mach-Zehnder modulator (DDMZM) are employed to generate SSB or pre-CD signal in this experiment and their transmission performance is also evaluated. To further to improve the spectrum efficiency and reduce the cost, we also present a detailed comparison of applying three advanced modulation formats including pulse amplitude modulation-8 (PAM-8), carrier-less amplitude and phase modulation-64 QAM (CAP-64), and discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S OFDM) with a bandwidth-limited direct-detection receiver for 100 Gb/s/λ optical transmission systems. The comparison is carried out to evaluate the performance of each modulation format in terms of nonlinear equalization, received optical power and optical signal to noise ratio (OSNR).
We summarize the enabling technologies for broadband millimeter-wave communication at W-band. These enabling technologies include photonics-aided broadband signal generation, high-spectral efficiency modulation format, multiple-input multiple-output (MIMO) reception, high gain antenna, optical and electrical multi-carrier modulation, antenna polarization multiplexing and multi-band multiplexing, advanced digital signal processing (DSP), and heterodyne detection. Based on these advanced technologies, we have realized over 400G wireless signal transmission and over 2.5-km wireless delivery with a bit rate up to 50Gb/s at W-band.
KEYWORDS: Sensors, Optical amplifiers, Fiber amplifiers, Signal detection, Radio over Fiber, Eye, Data communications, Receivers, Telecommunications, Optical engineering
We propose and experimentally demonstrate four-level pulse-amplitude-modulation (PAM-4) signal delivery in a radio-over-fiber system for the first time. Over 8-Gbit/s PAM-4 signals have been transmitted over 20-km single-mode fiber-28 and 1-m wireless distance. The signal after transmission is detected directly by an envelope detector at the receiver side. The maximal bit rate could be increased if the bandpass amplifier and envelope detector have more bandwidth.
KEYWORDS: Modulation, Radio over Fiber, Orthogonal frequency division multiplexing, Frequency division multiplexing, Optical amplifiers, Digital signal processing, Lithium, Fiber amplifiers, Optical engineering, Antennas
DFT-S-orthogonal frequency division multiplexing (OFDM) and single-carrier (SC) modulation are two typical modulation formats in radio-over-fiber (RoF) systems. They may have respective advantages and disadvantages in different scenarios. Therefore, bit error ratio comparison results of these two modulation formats will be useful for designing and optimizing the practical RoF system. We experimentally compare these two modulation formats in a long wireless distance RoF system at W-band. It can be concluded that DFT-S-OFDM and SC modulation have similar performances in a RoF system with transmission distance over 80-km fiber and 224-m wireless link.
KEYWORDS: Modulation, Dense wavelength division multiplexing, Single mode fibers, Absorption, Digital signal processing, Lithium, Signal to noise ratio, Fourier transforms, Forward error correction, Optical filters
We experimentally demonstrate 4 lanes up to 400 Gbps discrete multitone transmission using an electric absorption modulated laser (EML) at 1550-nm for dense wavelength division multiplexing (DWDM) intradata center connects. This is the first demonstration of 4×100 Gb/s transmission using EML at 1550-nm, and it is compatible with the DWDM system at C-band.
The nonlinear compensation algorithm based on Volterra series has been proved effective in low order modulation OFDM system, such as QPSK/16QAM. In this paper, we demonstrate a 64QAM/ 128QAM DFT-S-OFDM signal generation with DML with some advanced algorithms such as DD-LMS, ISFA, DFT-S and nonlinear compensation to improve the signal performance. For the first time we demonstrate that the nonlinear compensation algorithm based on Volterra series can improve the performance of the high-order modulation DFT-S-OFDM signal such as 64QAM and 128QAM. In this experiment we have realized 19.1/11.2Gb/s 64/128QAM signal transmission over 15km fiber at 1307nm. For 64QAM case, the receiver sensitivity can be improved about 1dB when all the algorithms mentioned in this paper are adopted. And the BER can be improved from 4.7x10-3 to 2.8x10-3 at 7.0dBm for 128QAM signal, which reaches the HD-FEC threshold of 3.8x10-3.
KEYWORDS: Extremely high frequency, Radio over Fiber, Analog electronics, Receivers, Modulation, Radio optics, Orthogonal frequency division multiplexing, Network architectures, Signal detection, Signal generators
Fifth-generation (5G) wireless access network promises to support higher access data rate with more than 1,000 times capacity with respect to current long-term evolution (LTE) systems. New radio-access-technologies (RATs) based on higher carrier frequencies to millimeter-wave (MMW) radio-over-fiber, and carrier-aggregation (CA) using multi-band resources are intensively studied to support the high data rate access and effectively use of frequency resources in heterogeneous mobile network (Het-Net). In this paper, we investigate several enabling technologies for MMW RoF systems in 5G Het-Net. Efficient mobile fronthaul (MFH) solutions for 5G centralized radio access network (C-RAN) and beyond are proposed, analyzed and experimentally demonstrated based on the analog scheme. Digital predistortion based on memory polynomial for analog MFH linearization are presented with improved EVM performances and receiver sensitivity. We also propose and experimentally demonstrate a novel inter-/intra- RAT CA scheme for 5G Het- Net. The real-time standard 4G-LTE signal is carrier-aggregated with three broadband 60GHz MMW signals based on proposed optical-domain band-mapping method. RATs based on new waveforms have also been studied here to achieve higher spectral-efficiency (SE) in asynchronous environments. Full-duplex asynchronous quasi-gapless carrier aggregation scheme for MMW ROF inter-/intra-RAT based on the FBMC is also presented with 4G-LTE signals. Compared with OFDM-based signals with large guard-bands, FBMC achieves higher spectral-efficiency with better EVM performance at less received power and smaller guard-bands.
KEYWORDS: Modulation, Signal generators, Single sideband modulation, Double sideband modulation, Radio optics, Single mode fibers, Digital signal processing, Laser sintering, Clocks, Receivers
We proposed single-sideband (SSB) quadrature phase-shift keying (QPSK) vector radio-frequency optical signal generation enabled by a single directly modulated laser without precoding technology, which can reduce the system cost and tolerate fiber dispersion. Based on our proposed scheme, we experimentally demonstrated 8-Gbaud SSB QPSK signals generation at 10 GHz, and the generated signals are transmitted over 50-km single-mode fiber without power penalty. Our experimental results show that an equal power SSB signal can tolerate fiber dispersion and have the highest receiver sensitivity.
KEYWORDS: Digital signal processing, Optical networks, Modulation, Transmitters, Receivers, Data communications, Adaptive optics, Telecommunications, Singular optics, Forward error correction, Signal detection, Multiplexers, Single mode fibers, Signal generators, Channel projecting optics
Digital signal processing (DSP) has been proved to be a successful technology recently in high speed and high spectrum-efficiency optical short-haul and access network, which enables high performances based on digital equalizations and compensations. In this paper, we investigate advanced DSP at the transmitter and receiver side for signal pre-equalization and post-equalization in an optical access network. A novel DSP-based digital and optical pre-equalization scheme has been proposed for bandwidth-limited high speed short-distance communication system, which is based on the feedback of receiver-side adaptive equalizers, such as least-mean-squares (LMS) algorithm and constant or multi-modulus algorithms (CMA, MMA). Based on this scheme, we experimentally demonstrate 400GE on a single optical carrier based on the highest ETDM 120-GBaud PDM-PAM-4 signal, using one external modulator and coherent detection. A line rate of 480-Gb/s is achieved, which enables 20% forward-error correction (FEC) overhead to keep the 400-Gb/s net information rate. The performance after fiber transmission shows large margin for both short range and metro/regional networks. We also extend the advanced DSP for short haul optical access networks by using high order QAMs. We propose and demonstrate a high speed multi-band CAP-WDM-PON system on intensity modulation, direct detection and digital equalizations. A hybrid modified cascaded MMA post-equalization schemes are used to equalize the multi-band CAP-mQAM signals. Using this scheme, we successfully demonstrates 550Gb/s high capacity WDMPON system with 11 WDM channels, 55 sub-bands, and 10-Gb/s per user in the downstream over 40-km SMF.
KEYWORDS: Digital signal processing, Field programmable gate arrays, Orthogonal frequency division multiplexing, Modulation, Receivers, Wavelength division multiplexing, Single mode fibers, Signal attenuation, Optical amplifiers, Laser sintering
In this paper, we review our recent research progresses on real-time orthogonal frequency division
multiplexing (OFDM) transmission based on FPGA. We successfully demonstrated four-channel
wavelength-division multiplexing (WDM) 256.51Gb/s 16-ary quadrature amplitude modulation
(16QAM)-OFDM signal transmission system for short-reach optical amplifier free inter-connection with
real-time reception. Four optical carriers are modulated by four different 16QAM-OFDM signals via
10G-class direct modulation lasers (DMLs). We achieved highest capacity real-time reception optical OFDM
signal transmission over 2.4-km SMF with the bit-error ratio (BER) under soft-decision forward error
correction (SD-FEC) limitation of 2.4×10-2. In order to achieve higher spectrum efficiency (SE), we
demonstrate 4-channel high level QAM-OFDM transmission over 20-km SMF-28 with real-time reception.
58.72-Gb/s 256QAM-OFDM and 56.4-Gb/s 128QAM-OFDM signal transmission within 25-GHz grid is
achieved with the BER under 2.4×10-2 and real-time reception.
We achieve several field trial demonstrations of ultra-wideband W-band millimeter-wave (mm-wave) signal generation and its long-distance air space transmission based on some enabling technologies and advanced devices. First, we demonstrated photonics generation and up to 1.7-km wireless delivery of 20-Gb/s polarization division multiplexing quadrature phase shift keying (PDM-QPSK) signal at W-band, adopting both optical and antenna polarization multiplexing. Then, we demonstrated photonics generation and up to 300-m wireless delivery of 80-Gb/s PDM-QPSK signal at W-band, adopting both optical and antenna polarization multiplexing as well as multi-band multiplexing. We also demonstrated photonics generation and up to 100-m wireless delivery of 100-Gb/s QPSK signal at W-band, adopting antenna polarization multiplexing.
KEYWORDS: Signal generators, Phase shift keying, Modulation, Modulators, Single mode fibers, Radio over Fiber, Lithium, Signal processing, Transmitters, Continuous wave operation
We numerically and experimentally investigate high-speed quadrature phase shift keying (QPSK) vector signal generation based on a single Mach–Zehnder intensity modulator employing a precoding technique. We experimentally demonstrate 16-Gbaud QPSK vector signal generation at 16-GHz carrier adopting optical carrier suppression with precoding technique, and it is the highest baud rate generated by this technology. The 16-Gbaud QPSK modulated vector signal is delivered over a 20-km large effective area fiber or 2-km single-mode fiber with a bit-error-rate less than the hard-decision forward-error-correction threshold of 3.8×10−3.
KEYWORDS: Digital signal processing, Orthogonal frequency division multiplexing, Field programmable gate arrays, Receivers, Modulation, Signal detection, Polarization, Singular optics, Transmitters, Optical filters
In this paper, we review our recent research progresses on real-time orthogonal frequency division multiplexing (OFDM) transmission and reception. We successfully realized the transmission and reception of real-time 100Gbps dual optical carrier 16-ary quadrature amplitude modulation (16QAM)-OFDM with direct detection for ultra-short fiber transmission. And we also successfully demonstrated the transmission and reception of real-time 100Gbps single-band coherent optical dual polarization (DP)-16QAM-OFDM signal for the first time with coherent detection. The measured bit error ratio (BER) for 100Gbps single-band coherent optical DP-16QAM-OFDM signal is less than 3.8×10-3 after 200-km standard single mode fiber (SSMF) without electrical dispersion compensation (EDC).
Super-Nyquist, also known as Fast-than-Nyquist (FTN), signal generation based on optical or electrical spectrum
shaping methods has been demonstrated to be an efficient scheme for future high-capacity transmission systems. Super-
Nyquist signal demodulations based on maximum a posteriori (MAP) or maximum likelihood sequence estimation
(MLSE) on receiver side have been demonstrated in 100G, 200G and 400G systems, which enables PDM-QPSK
transmission with 4bit/s/Hz net spectral efficiency (SE) at lower OSNR requirement and longer transmission distance.
Further studies also show the highly filtering-tolerant advantage of the super-Nyquist signal when using the 9-QAMbased
multi-modulus equalization. This feature is quite useful for signals transmission under the aggressive optical
filtering in multiple reconfigurable optical add-drop multiplexers (ROADMs) transmission link. In this paper, we review
the newly reported super-Nyquist experiments using the optical super-Nyquist filtering 9-QAM like signals based on
multi-modulus equalization (MMEQ). We directly recover the Nyquist filtered QPSK to a 9-QAM like signal. We first
successfully transmitted 100-GHz-grid, 20 channels single-carrier 440-Gb/s super-Nyquist 9-QAM-like signal over
3600-km ultra-large effective-area fiber (ULAF) at record a net SE of 4b/s/Hz (after excluding the 7% hard-decision
FEC overhead). The highly filtering-tolerant performance of the 9-QAM liked super-Nyquist signal is also
experimentally demonstrated. Using this scheme, we then successfully transmit 10 channels 440-Gb/s signal over 3000-
km ULAF and 10 cascaded ROADMs with 100-GHz-grid based on the single-carrier ETDM 110-GBaud QPSK. It is the
highest baud rate of all-ETDM signal reported with the highest net SE at this baud rate for PDM-QPSK signal.
Digital signal processing (DSP) for high spectrum efficiency transmission system are investigated in both long-haul and short haul optical networks. For long-haul transmission, two different super-Nyquist WDM systems based on advanced post (receiver side) and pre (transmitter side) DSP are demonstrated and studied. A novel DSP scheme for this optical super-Nyquist filtering 9-QAM like signals based on multi-modulus equalization (MMEQ) without post filter are proposed and experimentally demonstrated, which directly recovers the Nyquist filtered QPSK to a 9-QAM like signal. This improved filtering tolerance and transmission performance are demonstrated in an 8-channel 112-Gb/s wavelengthdivision- multiplexing (WDM) experiment with a 25GHz-grid over 2640-km single-mode fiber (SMF). Alternatively, a novel digital super-Nyquist signal generation scheme is proposed to further suppress the Nyquist signal bandwidth and reduce the channel crosstalk without using optical pre-filtering and using. Only optical couplers are needed for super- Nyquist WDM multiplexing. Using this scheme, we successfully generate and transmit 10 channel 32-GBaud (128-Gb/s) PDM-9-QAM signals within 25-GHz grid over 2975-km at a net SE of 4 bit/s/Hz (after excluding the 20% soft-decision FEC overhead). We extend the DSP for short haul optical transmission networks by using high order QAMs. We propose and experimentally demonstrate a high speed CAP-64QAM system using direct modulation laser (DML) based on direct detection and digital equalizations. Decision-directed least mean squares (DD-LMS) are used to equalize the CAP- 64QAM. Using this scheme, we successfully generate and transmit up to a record 60-Gb/s CAP-64QAM over 20-km stand single-mode fiber (SSMF) based on the DML and direct detection.
The implementations of super-Nyquist pulse generation, both in a digital field using a digital-to-analog converter (DAC) or an optical filter at transmitter side, are introduced. Three corresponding signal processing algorithms at receiver are presented and compared for high spectral-efficiency (SE) optical systems employing the spectral prefiltering. Those algorithms are designed for the mitigation towards inter-symbol-interference (ISI) and inter-channel-interference (ICI) impairments by the bandwidth constraint, including 1-tap constant modulus algorithm (CMA) and 3-tap maximum likelihood sequence estimation (MLSE), regular CMA and digital filter with 2-tap MLSE, and constant multi-modulus algorithm (CMMA) with 2-tap MLSE. The principles and prefiltering tolerance are given through numerical and experimental results.
We propose and experimentally demonstrate several different approaches for the realization of over 100Gb/s fiberwireless integration system, including optical PDM combined with MIMO reception, advanced multi-level modulation, optical multi-carrier modulation, electrical multi-carrier modulation, antenna polarization multiplexing and multi-band multiplexing. These approaches can effectively reduce the signal baud rate as well as the required bandwidth for optical and electrical devices. We also experimentally investigate the problems, such as multi-path effect due to different wireless transmission distance, existing in the large capacity fiber-wireless integration system. We experimentally demonstrate these problems can be effectively solved by advanced DSP algorithms including classic CMA.
Successful joint experiments with Deutsche Telecom (DT) on long-haul transmission of 100G and beyond are
demonstrated over standard single mode fiber (SSMF) and inline EDFA-only amplification. The transmission link
consists of 8 nodes and 950-km installed SSMF in DT’s optical infrastructure with the addition of lab SSMF for
extended optical reach. The first field transmission of 8×216.4-Gb/s Nyquist-WDM signals is reported over 1750-
km distance with 21.6-dB average loss per span. Each channel modulated by 54.2-Gbaud PDM-CSRZ-QPSK signal
is on 50-GHz grid, achieving a net spectral efficiency (SE) of 4 bit/s/Hz. We also demonstrate mixed data-rate
transmission coexisting with 1T, 400G, and 100G channels. The 400G uses four independent subcarriers modulated
by 28-Gbaud PDM-QPSK signals, yielding the net SE of 4 bit/s/Hz while 13 optically generated subcarriers from
single optical source are employed in 1T channel with 25-Gbaud PDM-QPSK modulation. The 100G signal uses
real-time coherent PDM-QPSK transponder with 15% overhead of soft-decision forward-error correction (SD-FEC).
The digital post filter and 1-bit maximum likelihood sequence estimation (MLSE) are introduced at the receiver
DSP to suppress noise, linear crosstalk and filtering effects. Our results show the future 400G and 1T channels
utilizing Nyquist WDM technique can transmit long-haul distance with higher SE using the same QPSK format.
KEYWORDS: Digital signal processing, Receivers, Polarization, Transmitters, Heterodyning, Modulation, Radio optics, Antennas, Signal detection, Modulators
In this invited paper, we experimentally demonstrate a seamlessly integrated fiber-wireless system that delivers 108-Gb/s
signal through 80-km fiber and 1-m wireless transport over free-space at 100 GHz, adopting polarization-divisionmultiplexing
quadrature-phase-shift-keying (PDM-QPSK) modulation and heterodyning coherent detection. The X- and
Y-polarization baseband components of the optical PDM-QPSK are simultaneously up-converted to 100-GHz wireless
carriers by optical polarization-diversity heterodyne beating, and then independently transmitted and received by two
pairs of transmitter and receiver antennas, which forms a 2x2 multiple-input multiple-output (MIMO) wireless link. At
the wireless receiver, two-stage down conversion is performed with firstly done in analog domain based on balanced
mixer and sinusoidal radio frequency (RF) signal, and then in digital domain based on digital signal processing (DSP).
MIMO signal de-multiplexing combined with optical polarization multiplexing and free space MIMO crosstalk is
realized by constant modulus algorithm (CMA) in digital signal processing (DSP) part at the receiver. The bit-error ratio
(BER) for the 108-Gb/s PDM-QPSK signal is less than the pre-forward-error-correction (pre-FEC) threshold of 3.8x10-3
after both 1-m wireless delivery at 100 GHz and 80-km single-mode fiber-28 (SMF-28) transmission. To our knowledge,
this is the first demonstration to realize 100-Gb/s signal delivery through both fiber and wireless links at 100GHz.
KEYWORDS: Modulation, Modulators, Phase modulation, Signal detection, Optical amplifiers, Signal generators, Digital signal processing, Polarization, Wavelength division multiplexing, Binary data
We summarize several advanced modulation formats for high capacity transmission system with high spectral efficiency.
We show that multilevel 8QAM, 16QAM, 32QAM and 64QAM optical signals can be generated by commercial optical
and electrical devices. Employing these multilevel modulation formats, we have realized PDM-36QAM 64Tb/s signals
transmission over 320km fiber. We also present some experimental results of 1Tb/s and 10Tb/s per channel signal
transmission by advanced modulation formats.
KEYWORDS: Modulators, Orthogonal frequency division multiplexing, Modulation, Laser sintering, Single mode fibers, Digital signal processing, Passive optical networks, Radio over Fiber, Signal processing, Network architectures
We demonstrate a novel low-cost radio-over-fiber network architecture with one directly modulated laser and one intensity modulator. By employing an orthogonal frequency division mutiplexing modulation format and frequency quadruple scheme, the bandwidth requirement of the devices and the cost of the system is reduced. Experimental results show that the power penalty for the downlink data after transmission over 20-km single mode optical fiber (SMF)-28 is smaller than 1.3 dB, while for the up-link data, the power penalty after transmission over 20-km SMF-28 is smaller than 0.3 dB.
KEYWORDS: Modulators, Modulation, Optical amplifiers, Polarization, Signal generators, Dense wavelength division multiplexing, Phase modulation, Signal detection, Receivers, L band
We successfully generated 114-Gb/s PDM-8QAM optical signal by novel scheme. Intradyne coherent detection of
PDM-8QAM optical signal with robust blind polarization de-multiplexing has been demonstrated by using a new cascaded
multi-modulus equalization algorithm. With RZ-shaped PDM-8QAM modulation and the proposed blind polarization
de-multiplexing algorithm, we demonstrate a record 33.9-Tb/s fiber capacity (320×114Gb/s) being transmitted over 580km
of ultra-low-loss SMF-28 fiber utilizing C+L-band EDFA-only optical amplification and single-ended coherent detection
technique, at a spectral efficiency of 4.2bit/s/Hz. Utilizing only C-band EDFA, we also demonstrate that 16.9-Tb/s capacity
(160×114Gb/s)) can be transmitted over 640km of standard SMF-28 fiber.
This paper describes convergence of optical and wireless access networks for delivering high-bandwidth integrated
services over optical fiber and air links. Several key system technologies are proposed and experimentally demonstrated.
We report here, for the first ever, a campus-wide field trial demonstration of radio-over-fiber (RoF) system transmitting
uncompressed standard-definition (SD) high-definition (HD) real-time video contents, carried by 2.4-GHz radio and 60-
GHz millimeter-wave signals, respectively, over 2.5-km standard single mode fiber (SMF-28) through the campus fiber
network at Georgia Institute of Technology (GT). In addition, subsystem technologies of Base Station and wireless
tranceivers operated at 60 GHz for real-time video distribution have been developed and tested.
For the first time, we experimentally investigated and demonstrated waveband switching for 100 Gb/s DWDM system
with high spectral efficiency of 3.4 b/s/Hz. 3 adjacent 25 GHz-spaced 114 Gb/s PolMux-RZ-8PSK channels are grouped
as a waveband to be switched and transmitted through 4 WSS-based ROADM nodes. Error free transmission is achieved
with little filtering effect observed even after 4 ROADM nodes. The transmission performance shows that waveband
switching based on WSS can be used in high spectral efficiency DWDM systems. This can reduce the switching
hardware cost and operation expense in highly dense WDM systems.
KEYWORDS: Digital signal processing, Orthogonal frequency division multiplexing, Modulation, Polarization, Signal detection, Receivers, Optical communications, Multiplexing, Signal processing, Optical fibers
We introduce two important technologies for development of next generation ultra-high-speed optical communications:
(i) polarization multiplexing, phase modulation with digital coherent detection, and (ii) OFDM-based optical fiber
transmission. In both schemes, digital signal processing plays a key role in recovering the signal and mitigating the
detrimental effects from optical signal transmission. We further describe a novel three dimensional low-density parity
check (LDPC) coded modulation scheme, including its principle and system performance.
We have designed and experimentally demonstrated optical networking technologies for generating, transmitting
and switching 100Gbit/s packet signals in optical networks. The performance of 100Gb/s packet transmission over
cascaded ROADM nodes with WSSs and over label switched metro networks are discussed.
We have experimentally demonstrated how to generate, transmission and switching 100Gbit/s packet signals. The
performance of transmission, switching, and label erasure has also been evaluated.
Multimode interference (MMI) devices operating at high data rates are important for integrated optics and optical networks. Their 1×N splitting provides a basic functionality in these applications. Ultra-high speed data transmission at 40Gb/s per channel with a total bandwidth of 320Gb/s for all 8 output ports is demonstrated for the first time on a 1 × 8 photo-definable polymer-based MMI power splitter. The transmission integrity is confirmed by the bit-error-rate (BER) testing. To further determine the speed limitations of MMI devices, ultra-short pulse response of these devices is quantified. For example, for 20fs Gaussian input pulses into a 1×8 polymer-based MMI splitter, the output pulses are severely degraded in coupling efficiency (47%) and completely broken up in time and in space primarily due to inter-modal and intra-modal (waveguide) dispersions.
The combination of broadband optical access and core networks is considered to be one of the most promising solutions for end-to-end transportation of high bit-rate data, video, and voice signals across optical networks of the future. Optical label switching technology (OLS) is an important aspect of optical packet switching and it involves the extraction and processing of the labels so that the packets can be routed to their destinations. OLS enables the routing and forwarding of the ultra-high bit rate payloads from source to destination entirely in the optical domain, thus alleviating the need for expensive optical-to-electrical conversions for processing. We have developed key enabling technologies for merged core and access networks including optical label generation, label swapping, optical buffering, clock recovery and wavelength conversion. We have experimentally demonstrated that these enabling techniques that can provide efficient broadband services in the future access and core networks.
Recent progress toward implementing high-density, optical-digital building blocks necessary to accomplish efficient, end-to-end optical interconnect architecture on low cost FR-4 boards has been demonstrated. The optical interconnect system consists of fabricating an optical buffer layer separating board metallurgy from the optical lightwave circuit layer, and implementing optical links between embedded lasers and detectors. We will show an example of 1310 nm light from an edge emitting distributed-feedback or Fabry-Perot laser operating at 10 Gb/s being guided to the photo-detector by a polymer waveguide. Both lasers and detector are embedded in the waveguide and all construction is built on a low-cost FR-4 board with 3 levels of metallurgy.
We have experimentally demonstrated some key techniques in label switching optical networks. These techniques include optical label generation, optical label swapping and preamble free clock recovery. The label generation using optical carrier suppression and separation (OCSS) technique has these advantages of high bit rate operation, low cross-talk and narrow bandwidth occupancy. The label swapping is realized by combining OCSS and wavelength conversion. The payload can be simultaneously regenerated after wavelength conversion; hence this technique is very useful for cascaded label swapping in label switched optical networks. We have also demonstrated how to realize preamble free clock recovery for burst mode label and payload generated by OCSS technique.
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