Injection-locked Distributed Feedback Laser Research Articles

Two-Way 5G NR Fiber-Wireless Systems Using Single-Carrier Optical Modulation for Downstream and Phase Modulation Scheme for Upstream

Fifth-generation (5G) millimeter-wave (MMW)/sub-THz signals over a two-way fiber-wireless system using single-carrier optical modulation for downstream and phase modulation (PM) scheme for upstream are proposed and implemented for the first time. Compared to multi-carrier optical modulation, using single-carrier optical modulation in downlink is attractive because it can suppress RF power fading due to fiber dispersion and interference caused by optical beating from multiple carriers. Furthermore, compared to intensity modulation scheme, using PM scheme with remotely injection-locked distributed feedback laser diode in uplink is attractive because it enables high robustness to noise and distortion. Through 40-km single-mode fiber, 500-m free-space optical, and 2-m/1-m/0.5-m (downstream)/4-m (upstream) RF wireless cascaded-medium, 5G new radio (NR) MMW/sub-THz signals are transported with low bit error rates and clear constellations in downlink/uplink performance. Such a newly-built two-way 5G NR fiber-wireless system shows promise to perform 5G NR evolution in MMW and sub-THz frequencies, which has significant impacts on fiber-wireless integration.

A Flexible Bidirectional Fiber-FSO-5G Wireless Convergent System

A flexible bidirectional fiber-free-space optical (FSO)-fifth-generation (5G) wireless convergent system with 1-Gb/s/4.5-GHz sub-6 GHz and 10-Gb/s/28-GHz millimeter-wave (MMW) (downstream), as well as 10-Gb/s/24-GHz MMW (upstream) 5G hybrid data signals is built, employing a vertical cavity surface emitting laser (VCSEL)-based wavelength selector and a remotely injection-locked distributed feedback laser diode (DFB LD) for presentation. It is the first to adopt a VCSEL-based wavelength selector to adaptively provide 5G applications and an injection-locked DFB LD to perform a phase modulation-to-intensity modulation transformation with an optical-to-electrical conversion. Good bit error rate performance and acceptable eye diagrams are achieved over 25 km single-mode fiber transport, 600 m FSO link, and 10 m/4 m RF wireless transmission. Such demonstrated fiber-FSO-5G wireless convergent system is a promising one toward optical-based long-haul networks at comparatively high-speed operations. It exhibits an excellent convergence not only due to its development for incorporating optical fiber with optical/5G wireless networks, but also due to its enhancement for flexible two-way high-speed and long-haul communications.

A Bidirectional FSO Communication Employing Phase Modulation Scheme and Remotely Injection-Locked DFB LD

A bidirectional free-space optical (FSO) communication through a 600-m free-space transmission is built, employing a phase modulation (PM) scheme and a remotely injection-locked distributed feedback laser diode (DFB LD) for presentation. With optimum injection locking, a DFB LD is excellent for duplex transceiver operations. An injection-locked DFB LD not only operates as a PM-to-intensity modulation converter with an optical detector, but also functions as an upstream optical carrier. To be the first one of employing a remotely injection-locked DFB LD to detect a phase-modulated 25-Gb/s/25-GHz four-level pulse amplitude modulation (PAM4) passband signal, the DFB LD with remote injection locking is successfully intensity-modulated with an upstream 25-Gb/s non-return-to-zero (NRZ) signal. Good bit error rate performance and clear PAM4/NRZ eye diagrams show that this FSO communication can use a remotely injection-locked DFB LD to detect the downstream phase-modulated PAM4 signal and concurrently deliver an upstream intensity-modulated NRZ signal. This bidirectional 25-Gb/s/25-GHz (downstream)/25-Gb/s (upstream) FSO communication is prominent due to its enhancement in two-way high-speed optical wireless communications.

Bidirectional optical single-sideband modulation and phase remodulation radio-on-fiber transport systems with fiber nonlinearity and injection-locked laser technology

We propose a bidirectional transmission system based on stimulated Brillouin scattering effect and injection-locked distributed feedback laser to achieve an optical single-sideband modulation for downlink transmission. We reuse the transmitted light through phase modulation for uplink transmission to avoid interference of both signals in a bidirectional transport. After a 25-km single-mode fiber transmission is completed, a sideband power ratio of >15 dB is observed in the downlink transmission, and the power penalty of the system is <1 dB. In our proposed bidirectional transmission system, the performances of bit error rate analysis are good.

Modulation Characteristics Enhancement of Monolithically Integrated Laser Diodes Under Mutual Injection Locking

Modulation characteristics enhancement by mutual injection locking of monolithically integrated distributed feedback (DFB) lasers is studied. Locking bistability in mutually coupled integrated lasers is observed. Resonance frequency as high as 34.3 GHz is recorded, corresponding to more than fivefold enhancement over the relaxation oscillation frequency at free running state. The mutually injection-locked lasers exhibit reduced harmonics and third-order intermodulation distortion, as well as suppressed relative intensity noise near the relaxation oscillation frequency. The spurious-free dynamic range is improved from 75 to 80 dB·Hz2/3. Furthermore, alleviation of chirp-induced power fading in analog optical links has been demonstrated. To our knowledge, this is the first time that suppressed nonlinear distortion and noise as well as chirp reduction are simultaneously demonstrated for monolithic mutually injection-locked DFB lasers.

Three dispersion compensation methods for radio-over-fiber system

This paper introduces three different dispersion compensation methods based on superstructure fiber Bragg grating (SSFBG) and an injection distributed feedback (DFB) laser. First, an SSFBG with a nonlinearity group delay spectrum was designed to achieve tunable dispersion compensation. Second, an approach is pro- posed for realizing single-sideband modulation with an optimum optical carrier to sideband ratio for maximizing the transmission performance of a radio-over-fiber (RoF) system based on a strong optical injection-locked DFB laser. Finally, a broadband chromatic dispersion compensation scheme using an optical phase conjugator based on a DFB semiconductor laser is proposed and experimentally demonstrated in RoF links. © 2015 Society of Photo-

Optical single sideband modulation using fiber nonlinearity and injection locked technology in radio‐on‐fiber systems

ABSTRACTWe propose a transmission system based on stimulated Brillouin scattering (SBS) effect and injection locked distributed‐feedback (DFB) laser to achieve optical single sideband (OSSB) modulation. These two kinds of technologies fall on frequency band approximately nearby 10.8 GHz to enhance OSSB signal. The first step drives radio frequency signal into modulator and uses SBS effect to enhance right sideband. The second step based on injection locked DFB laser achieves OSSB modulation. After 25‐km single mode fiber transmission, we can observe the sideband power ratio &gt; 15.81 dB and performances for bit error rate analysis with power penalty about 5.2 dB at 10−8. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:274–278, 2014

A bidirectional lightwave transport system based on PON integration with WDM VLC

A novel bidirectional lightwave transport system employing phase modulation (PM) scheme and light injection-locked distributed feedback laser diode (DFB LD) as a duplex transceiver for passive optical network (PON); as well as employing laser pointer lasers (LPLs) with directly modulating data signals for wavelength-division-multiplexing (WDM) visible light communication (VLC) is proposed and experimentally demonstrated. Impressive and low bit error rate (BER) operation is achieved for PON integration with VLC application. Such bidirectional PON integration with VLC system has been successfully demonstrated, which can not only present its advancement in PON/VLC application but also reveal its simplicity and convenience to be installed. Whereby, our proposed system is suitably applicable to the PON in combination with VLC system in wire and wireless transmission.

Fiber optical CATV transport systems based on PM and light injection-locked DFB LD as a duplex transceiver

A bidirectional fiber optical CATV transport system employing phase modulation (PM) scheme and frequency up-conversion technique to deal with downstream CATV signals, and using light injection-locked distributed feedback laser diode (DFB LD) as a duplex transceiver at the receiving site is proposed and experimentally demonstrated. With optimum injection wavelength and power level, a DFB LD is efficiently employed for both the transmitter and receiver operations. Such DFB LD is used to replace the functions of delay interferometer (DI) and CATV receiver, and also to be as the upstream light source. To the best of our knowledge, it is the first time to successfully utilize a DFB LD to detect the phase-modulated CATV signals. Impressive experimental results prove that our proposed systems not only can employ the PM scheme and the frequency up-conversion technique to optimize the overall performances of systems, but also can use an injection-locked DFB LD to detect the downstream phase-modulated CATV signals as well as to transmit the upstream CATV ones simultaneously.

Visible-to-near infrared standard source generation using acetylene ( 13C 2H 2)-stabilized comb-injection-locked technique

An ultra-stable visible laser source (VLS) was generated by the second harmonic of a selectively injection-locked distributed feedback (DFB) laser from an optical frequency comb with acetylene-stabilized laser seeding. For the second-harmonic generation (SHG) of the injection-locked DFB laser, we used periodically poled lithium niobate (PPLN) crystal and generated the VLS at a region of 771 nm, which was discretely locked to a spacing of 25 GHz within the PPLN bandwidth (180 GHz). The frequency stability of this source was estimated to be 1.1 × 10 − 12 with an average time of 1 s.

Single-Sideband Modulation Based on an Injection-Locked DFB Laser in Radio-Over-Fiber Systems

We report an experimental demonstration of optical single-sideband (SSB) modulation in 60-GHz radio-over-fiber systems based on an injection-locked distributed-feedback (DFB) laser. Two heterodyning optical modes with 60-GHz spacing are injected into the DFB laser and one of them is used to lock the DFB laser. When the DFB laser is directly modulated, the modulation index of the locked mode is 15 dB larger than that of the unlocked one. The 2.5-Gb/s data transmission at 60 GHz is successfully achieved over 50-km standard single-mode fiber using the proposed SSB scheme.

Full-duplex radio-on-fiber transport systems based on main and multiple side modes injection-locked DFB laser diode

A full duplex radio-on-fiber (ROF) transport system based on main and multiple side modes injection-locked distributed feedback laser diode (DFB LD) is proposed and experimentally investigated. DFB LD is successfully injection-locked not only in the main mode but also in other side modes. A data signal of 70 Mbps/10 GHz (WiMAX) signal is transmitted over long-haul single-mode fiber (SMF) transmission. Good bit error rate (BER) performances were achieved for both down-link and up-link transmissions in our proposed full-duplex ROF transport systems.

Optical Properties and Modulation Characteristics of Ultra-Strong Injection-Locked Distributed Feedback Lasers

The optical properties and the frequency responses of ultrastrong (injection ratio > 10 dB) injection-locked distributed feedback lasers are investigated experimentally and theoretically. We have observed three distinctive modulation regimes under different frequency detuning between the master and the slave lasers. At large negative frequency detuning, the laser exhibits enhanced modulation efficiency at low frequencies. At intermediate frequency detuning, a flat frequency response with large 3 dB bandwidth is observed. At large positive frequency detuning, the modulation response shows a pronounced resonance peak at high frequencies. These phenomena can be explained by the resonance enhancement of the slave laser cavity mode, with the resonance frequency equal to the difference between the injection-locked frequency and the cavity mode. The experimental results agree well with theoretical calculations based on three coupled rate equations. Depending on the applications, the injection locking conditions can be optimized to achieve high RF link gain, broadband, or high resonance frequency operations.

1.3-$\mu$m Amplifier-Free All-Optical 2R Regenerator Using Two-Mode Injection-Locked Distributed Feedback Laser Diode

This study presents a novel and cost-effective 1.3-mum all-optical 2R regenerator based on a two-mode injection-locked distributed feedback laser diode. The proposed 2R regenerator, with 14.13-dB small signal gain, has achieved an amplifier-free 10-Gb/s straight line transmission over 60 km while keeping the power penalty less than 0.84 dB at bit-error rate (BER) =10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> . In addition, properties like BER degradation, output extinction ratio, gain, and data-rate transparency are also experimentally investigated

Demodulation of multi-gigahertz frequency-modulated optical signals in an injection-locked distributed feedback laser oscillator

A new type of wavelength selective optical receiver that allows the demodulation of multi-gigaHertz frequency modulated (FM) optical signals is demonstrated by detecting FM light-induced changes in the forward voltage of an optically injection-locked distributed feedback semiconductor laser operating at far above the lasing threshold. A bandwidth as wide as 2 GHz is reported together with an FM demodulation efficiency of 52 mu V/GHz. >