Light Injection Technique Research Articles

500 Gb/s PAM4 FSO-UWOC Convergent System With a R/G/B Five-Wavelength Polarization-Multiplexing Scheme

A 500-Gb/s four-level pulse amplitude modulation (PAM4) free-space optical (FSO)underwater wireless laser transmission (UWOC) convergent system over 100 m free-space transmission with either 10 m piped underwater link or 5 m turbid underwater link is established, employing a red/green/blue (R/G/B) five-wavelength polarization-multiplexing scheme as a demonstration for the first time. Integrating PAM4 modulation with five-wavelength polarization-multiplexing scheme, the channel capacity of FSOUWOC convergent systems is significantly increased with an aggregate data rate of 500 Gb/s [50 Gb/s PAM4/wavelength × 5 wavelengths × 2 polarizations (p- and s-polarizations)]. Results reveal that five R/G/B laser diode (LD) transmitters with two-stage light injection and optoelectronic feedback techniques are capably adopted for 500 Gb/s PAM4 signal transmission. Compared with prior FSO-UWOC convergence and visible light communication using polarization-multiplexing R/G/B LDs, it shows a prominent one with the benefits of high aggregate transmission rate and long-range optical wireless link. Excellent bit error rate performance and accepted PAM4 eye diagrams are attained over a 110-m/105-m FSO-UWOC link. This demonstrated five-wavelength polarization-multiplexing FSO-UWOC convergent system is promising because it not only integrates free-space backbone with underwater optical wireless feeder, but it also substantially multiplies total channel capacity.

A WDM PAM4 FSO–UWOC Integrated System With a Channel Capacity of 100 Gb/s

A wavelength-division-multiplexing (WDM) four-level pulse amplitude modulation (PAM4) free-space optical (FSO)–underwater wireless optical communication (UWOC) integrated system with a channel capacity of 100 Gb/s is proposed and attainably demonstrated. Analytic results reveal that 1.8-GHz 405-nm blue-violet-light and 1.7-GHz 450-nm blue-light laser diodes (LDs) with two-stage light injection and optoelectronic feedback techniques are competently adopted for 100 Gb/s PAM4 signal transmission through a 500-m free-space transmission with 5-m clear ocean underwater link. Combining dual-wavelength WDM scenario with PAM4 modulation, the channel capacity of FSO–UWOC integrated systems is significantly enhanced with an aggregate transmission rate of 100 Gb/s (25 Gbaud PAM4/wavelength × 2 wavelengths). With doublet lenses in FSO, laser beam reducer and transmissive spatial light modulator in UWOC, a sufficiently low bit error rate of 10−9 and acceptable PAM4 eye diagrams are acquired. This demonstrated 100 Gb/s PAM4 FSO–UWOC integrated system with a WDM scenario is advantageous for the enhancement of a high-speed optical wireless link with long-reach transmission.

Bidirectional and simultaneous transmission of baseband and wireless signals over RSOA based WDM radio-over-fiber passive optical network using incoherent light injection technique

Reflective semiconductor optical amplifier (RSOA) based wavelength division multiplexed radio-over-fiber passive optical network (WDM−RoF−PON) has been proposed and demonstrated, to transmit 2.5Gbps baseband (BB) and 1.25Gbps wireless data in downstream and 1Gbps BB data signal in upstream over 25-km single-mode fiber (SMF), and wireless downstream signal over 25-km SMF as well as 5.2m free space in air. In the downstream, 2.5Gbps BB data and 1.25Gbps wireless data are modulated using single-electrode Mach–Zehnder modulator (SD-MZM) based on double-sideband with optical carrier suppression (DSBCS) scheme and simultaneously transmitted by incoherent light injection technique and employing fiber Bragg grating (FBG) at the base station. RSOA is utilized at the user end to reuse the carrier for uplink transmission. High receiver sensitivity, low bit-error-rate (BER) and excellent eye-diagram, eye height are achieved in our proposed network system and the results affirm the acceptability of proposed RSOA based WDM−RoF−PON.

16 Gb/s PAM4 UWOC system based on 488-nm LD with light injection and optoelectronic feedback techniques.

A 16 Gb/s four-level pulse amplitude modulation (PAM4) underwater wireless optical communication (UWOC) system based on 488-nm laser diode (LD) with light injection and optoelectronic feedback techniques is proposed and successfully demonstrated. Experimental results show that such a 1.8-GHz 488-nm blue light LD with light injection and optoelectronic feedback techniques is enough forceful for a 16 Gb/s PAM4 signal underwater link. To the authors' knowledge, this study is the first to successfully adopt a 488-nm LD transmitter with light injection and optoelectronic feedback techniques in a PAM4 UWOC system. By adopting a 488-nm LD transmitter with light injection and optoelectronic feedback techniques, good bit error rate performance (offline processed by Matlab) and clear eye diagrams (measured in real-time) are achieved over a 10-m underwater link. The proposed system has the potential to play a vital role in the future UWOC infrastructure by effectively providing high transmission rate (16 Gb/s) and long underwater transmission distance (10 m).

A 103.12-Gb/s WDM PAM4 VCSEL-Based Transmission With Light Injection and Optoelectronic Feedback Techniques

A 103.12-Gb/s wavelength-division-multiplexing (WDM) four-level pulse amplitude modulation (PAM4) transmission based on 850-nm and 880-nm vertical-cavity surface-emitting lasers (VCSELs) with light injection and optoelectronic feedback techniques is proposed and experimentally demonstrated. Results show that two such 7.5-GHz VCSELs with light injection and optoelectronic feedback techniques are potent for 103.12-Gb/s WDM PAM4 transmissions. To the authors’ knowledge, it is the first one to successfully adopt two VCSEL transmitters with light injection and optoelectronic feedback techniques in a WDM PAM4 transmission. A total transmission rate of 103.12 Gb/s (51.56 Gb/s/λ × 2 λs) is achieved in the proposed WDM PAM4 transmissions. The link performances of the proposed WDM PAM4 transmissions have been evaluated in real time. Good real-time bit error rate performance and three independent clear eye diagrams are obtained at a 180-m OM4 multimode fiber operation. Such a proposed 103.12-Gb/s WDM PAM4 VCSEL-based transmission has great potential for providing efficient bandwidth in short-reach optical communications.

45 Gb/s PAM4 transmission based on VCSEL with light injection and optoelectronic feedback techniques.

A 45Gb/s four-level pulse amplitude modulation (PAM4) transmission based on an 850nm/7.4GHz vertical cavity surface emitting laser (VCSEL) with light injection and optoelectronic feedback techniques is proposed. Experimental results show that such an 850nm/7.4GHz VCSEL with light injection and optoelectronic feedback techniques is powerful enough for a 45Gb/s PAM4 signal transmission. To the best of our knowledge, this Letter is the first to adopt a VCSEL transmitter with light injection and optoelectronic feedback techniques in a 45Gb/s PAM4 transmission system. Good bit error rate performance and three independent clear eye diagrams are achieved over a 200-m OM4 multimode fiber transport. This proposed 45Gb/s PAM4 VCSEL-based transmission system has great potential for providing effective bandwidth in short-reach optical data communications.

A hybrid lightwave transmission system based on light injection/optoelectronic feedback techniques and fiber-VLLC integration

A hybrid lightwave transmission system based on light injection/optoelectronic feedback techniques and fiber-visible laser light communication (VLLC) integration is proposed and experimentally demonstrated. To be the first one of its kind in employing light injection and optoelectronic feedback techniques in a fiber-VLLC integration lightwave transmission system, the light is successfully directly modulated with Community Access Television (CATV), 16-QAM, and 16-QAM-OFDM signals. Over a 40 km SMF and a 10 m free-space VLLC transport, good performances of carrier-to-noise ratio (CNR)/composite second-order (CSO)/composite triple-beat (CTB)/bit error rate (BER) are achieved for CATV/16-QAM/16-QAM-OFDM signals transmission. Such a hybrid lightwave transmission system would be very useful since it can provide broadband integrated services including CATV, Internet, and telecommunication services over both distribute fiber and in-building networks.

A Bidirectional Hybrid Lightwave Transport System Based on Fiber-IVLLC and Fiber-VLLC Convergences

This paper proposes and validates a bidirectional hybrid lightwave transport system based on fiber-invisible laser light communication (IVLLC) and fiber-visible laser light communication (VLLC) convergences with light injection and optoelectronic feedback techniques. This paper is also the first to employ light injection and optoelectronic feedback techniques in a bidirectional lightwave transport system based on fiber-IVLLC and fiber-VLLC integration. Light is successfully modulated directly with cable television (CATV), 16-quadrature amplitude modulation (QAM), and 16-QAM-orthogonal frequency-division multiplexing (OFDM) signals. Good carrier-to-noise ratio, composite second order, composite triple beat, and bit error rate (BER) are obtained for CATV, 16-QAM, and 16-QAM-OFDM signal transmissions over a combined 40-km single-mode fiber, a 1.43-km photonic crystal fiber, and 6-m free-space transmission. The proposed bidirectional hybrid lightwave transport system exhibits significant potential in providing broadband integrated services, such as CATV, Internet, and telecommunication, via optical fiber and free-space indoor networks.

20-Gbps optical LiFi transport system.

A 20-Gbps optical light-based WiFi (LiFi) transport system employing vertical-cavity surface-emitting laser (VCSEL) and external light injection technique with 16-quadrature amplitude modulation (QAM)-orthogonal frequency-division multiplexing (OFDM) modulating signal is proposed. Good bit error rate (BER) performance and clear constellation map are achieved in our proposed optical LiFi transport systems. An optical LiFi transport system, delivering 16-QAM-OFDM signal over a 6-m free-space link, with a data rate of 20Gbps, is successfully demonstrated. Such a 20-Gbps optical LiFi transport system provides the advantage of a free-space communication link for high data rates, which can accelerate the visible laser light communication (VLLC) deployment.

Fiber Identification Below an Optical Splitter With a Test Light Injection Tool

We propose a novel test light injection tool for fiber identification below an optical splitter in a passive optical network. This tool makes it easy to input a test light into a bent fiber with a lateral light injection technique. We designed a high precision alignment technique to improve the test light injection efficiency and confirmed that the proposed tool can be used for fiber identification below an optical splitter.

Pattern Effect Suppression by Injecting Directly Modulated Synchronized Gain-Clamping Light Using Inverted Signal for PON Application of SOA

This paper presents and demonstrates a simple pattern effect suppression technique for the downstream repeater and the upstream booster semiconductor optical amplifiers (SOAs) of an SOA-based, optically amplified passive optical network (PON) system. The synchronized gain-clamping light injection technique is applied to an SOA mainly consisting of an optical-electrical-optical converter. The feasibility of the technique is confirmed experimentally by applying it to a downstream amplification repeater in a Gigabit Ethernet PON (GE-PON) and a upstream booster amplifier in a 10G-EPON with a high output power optical network unit (ONU). In both cases, the pattern effect is significantly suppressed and the system loss budget is greatly improved. For the GE-PON repeater a large access span loss of over 40 dB was achieved with a trunk span distance of 51.8 km, and for the 10G-EPON the loss budget was increased to over 40 dB by using high-output power ONU.

Dispersion penalty analysis using light injection method in the feedforward optical transmitter for WDM/SCM radio-over-fiber systems

We have experimentally and theoretically demonstrated the transmission performance of a feedforward optical transmitter using an external light injection technique. The feedforward compensation method shows 31 dB intermodulation distortion suppression and 2.2 dB noise reduction. The feedforward architecture used a wavelength-locked Fabry–Perot laser diode whose side-mode suppression ratio about 35 dB over a 12-nm range. The suppression characteristics of the intermodulation distortion for various wavelength differences and transmission lengths were measured and analyzed as the evaluation criteria for the system performance in WDM/SCM based radio-over-fiber systems.

CATV/ROF transport systems based on light injection/optoelectronic feedback techniques and photonic crystal fiber

A directly modulated CATV/radio-on-fiber (ROF) transport system based on light injection and optoelectronic feedback techniques, and photonic crystal fiber (PCF) is proposed and demonstrated. Excellent performances of carrier-to-noise ratio (CNR), composite second order (CSO) and composite triple beat (CTB) were obtained for CATV band; as well as low bit error rate (BER) and third order intermodulation distortion to carrier ratio (IMD 3/ C) values were achieved for ROF band. This demonstrated that such a CATV/ROF transport system is very attractive for the fiber backbone applications.

Directly modulated fiber optical CATV transport systems without optical amplification

We propose and demonstrate a repeaterless directly modulated fiber optical CATV transport system based on half-split-band and remote light injection techniques. Good performances of carrier-to-noise ratio (CNR), composite second order (CSO) and composite triple beat (CTB) were obtained over a 50-km single mode fiber (SMF) transmission without optical amplification. Our proposed repeaterless directly modulated fiber optical CATV transport systems are simpler and cost lower than conventional externally modulated ones.

Fiber-optical cable television system performance improvement employing light injection and optoelectronic feedback techniques

A split-band directly modulated fiber-optical cable television system employing light injection and optoelectronic feedback techniques is proposed and demonstrated. The light injection technique enhances the laser resonance frequency, and the optoelectronic feedback technique further enhances it, leading to an improvement in the systems' overall performances. Good performances of carrier-to-noise ratio, composite second order, and composite triple beat were achieved for the full channel band over a 100-km single-mode fiber transport

Linearization of DFB laser diode by external light-injected cross-gain modulation for radio-over-fiber link

A novel linearization technique of distributed-feedback laser diode in analog optical transmitter for radio-over-fiber (RoF) link was proposed. The proposed scheme was based on a light-injection technique using cross-gain modulation effect. According to the proposed idea, a linearized RoF transmitter module was implemented and evaluated. The enhanced performance of carrier-to-noise ratio and spurious-free dynamic range were experimentally demonstrated in a wide range of radio-frequency (RF) applications. The experimental results show that the proposed scheme can be applicable for broadband RF optical transmission applications.

Improvement of radio-on-multimode fiber systems based on light injection and optoelectronic feedback techniques

A radio-on-multimode fiber (MMF) system based on vertical-cavity surface-emitting lasers (VCSELs) injection-locked and optoelectronic feedback techniques is proposed and demonstrated. Injection locking and optoelectronic feedback achieves large frequency response of the VCSEL, resulting in good performances of intermodulation distortion to carrier ratio (IMD/C), error vector magnitude (EVM), and bit error rate (BER). Using VCSELs as optical sources in radio-on-MMF systems are very attractive, as they are relatively simple to fabricate and potentially low-cost. Such a proposed radio-on-MMF system is suitable for the short-haul microwave optical links.

Dynamic characteristics of long-wavelength quantum dot vertical-cavity surface-emitting lasers with light injection

This investigation experimentally demonstrates the dynamic characteristics of quantum dot vertical-cavity surface-emitting lasers (QD VCSEL) without and with light injection. The QD VCSEL is fully doped structure on GaAs substrate and operates in the 1.3 mum optical communication wavelength. The eye diagram, frequency response, and intermodulation distortion are presented. We also demonstrate that the frequency response enhancement by light injection technique allows us to improve the performance of subcarrier multiplexed system.

A bidirectional radio-on DWDM transport system for LAN and ITS applications

A bidirectional radio-on dense-wavelength-division-multiplexing (DWDM) transport system based on external light injection technique and adaptive filters is proposed. Not only were a low bit-error rate and error vector magnitude obtained, but also good performance of third-order intermodulation distortion to carrier ratio (IMD/sub 3//C) was achieved for local area network (LAN) and intelligence transport system (ITS) applications.

A CATV Lightwave Transport System Based on Fabry-Perot Laser and External ASE Light Injection Technique

We propose a low cost WDM optical source using split band technology and external ASE light injection for CATV signals transmission. Good performance of carrier-to-noise ratio (CNR), composite second order (CSO) and composite triple beat (CTB) were observed over 30 km SMF transmission.