Fabry-Perot Laser Diode Research Articles

Multiple fiber Bragg grating sensing system based on active mode-locking fiber laser

In this paper, a new multiple fiber Bragg grating (FBG) sensing system based on active mode-locking fiber laser is proposed. The active mode-locking fiber laser is composed of a linear cavity with an Fabry–Perot laser diode (F-P LD) as a reflective cavity mirror, and the erbium-doped fiber as the gain medium. Meanwhile, the F-P LD is also used as the modulating element of the fiber laser. Multiple FBGs cascaded in a long fiber are used as both the sensors in the system and the components for wavelength selection in the active mode-locking fiber laser. The capacity of the proposed sensing system to interrogate multiple FBGs in wavelength and spatial domain is investigated. The proposed sensing system has the characteristics of low cost, good stability, good compatibility, and can be used in quasi-distributed multi-point sensing.

Indistinguishable sub-nanosecond pulse generator

The indistinguishable laser pulse is predominant in the realization of qubits in decoy state-based quantum cryptography. Such cryptography in an automotive framework needs to be compact and inexpensive. However, their implementation is cumbrous and uneconomical. Significant effort has been put into reducing the form factor of quantum cryptography implementation. We report a compact, low-cost, indistinguishable, sub-nanosecond pulse generator with adjusted delay and amplitude using a Fabry–Perot laser diode. The approach was derived based on algebraic topology formulation of the electrical network, and the implementation involves time-dependent perturbation of a constant current node to generate tunable, sub-nanosecond excitation with a constant pre-bias. The simulation model of the laser diode accounted for effects of spontaneous emission and relaxation oscillation. The shortest excitation pulse thus generated was measured to have FWHM of 496 ps. Further, the indistinguishability of two laser pulses is statistically evaluated.

Coherence function-encoded optical palpation.

Optical palpation maps stress at the surface of biological tissue into 2D images. It relies on measuring surface deformation of a compliant layer, which to date has been performed with optical coherence tomography (OCT). OCT-based optical palpation holds promise for improved clinical diagnostics; however, the complexity and cost hinder broad adoption. In this Letter, we introduce coherence function-encoded optical palpation (CFE-OP) using a novel optical profilometry technique that exploits the envelope of the coherence function rather than its peak position, which is typically used to retrieve depth information. CFE-OP utilizes a Fabry-Perot laser diode (bandwidth, 2.2 nm) and a single photodiode in a Michelson interferometer to detect the position along the coherence envelope as a function of path length. This technique greatly reduces complexity and cost in comparison to the OCT-based approach. We perform CFE-OP on phantom and excised human breast tissue, demonstrating comparable mechanical contrast to OCT-based optical palpation and the capability to distinguish stiff tumor from soft benign tissue.

High-Speed Switchable Dual-Passband Microwave Photonic Filter With Dual-Beam Injection in an SMFP-LD

In this paper, a high-speed switchable dual-passband microwave photonic filter (MPF) using a single mode Fabry-Perot laser diode (SMFP-LD) is proposed and experimentally demonstrated. Benefiting from the wavelength selective amplification in the SMFP-LD, the +1 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">st</sup> sideband of two external beams injected after phase modulation can be amplified in the gain spectrum of the SMFP-LD. Hence, an MPF with two tunable passbands is generated. The switching of the generated passbands is obtained through the switching signal of 1 Gbps applied to the modulator, which controls the power of one of the external beams. By properly setting the external beams’ injection parameters, the passbands of MPF can switch from single passband to no passband, single passband to dual passband, and one passband to another passband. In this experiment, the maximum center frequency and tuning range of the passbands is 45.0 GHz and 35.0 GHz, respectively. The out-of-band rejection ratio and 3 dB bandwidth of the proposed filter are 29.62 dB and 83 MHz, respectively.

Optically-Injected-Semiconductor-Laser-Based Tunable Dual-Frequency Optoelectronic Oscillator under Subharmonic Microwave Modulation

To obtain low-phase-noise microwave signals with a widely tunable frequency range, an optoelectronic oscillator (OEO) was constructed on the basis of an optically injected semiconductor laser (OISL) for the generation of high-quality microwave signals. Our OEO relied on the effect of wavelength-selective amplification and the period-one (P1) oscillation under optical injection. The signal’s frequency stability, side-mode-suppression ratio (SMSR) and linewidth were optimized by the subharmonic microwave modulation technique in the OEO loop. The experimental results showed that the frequency of the signal obtained by the proposed OEO could be tuned up to 18 GHz. Using the dual-loop OEO structure, the SMSR was increased to 55 dB. Moreover, the phase noise of the obtained microwave signal was lower than −81 dBc/Hz at 1 kHz frequency offset and −119 dBc/Hz at 10 kHz frequency offset. This was achieved by introducing subharmonic microwave modulation in the OEO loop, respectively. Furthermore, via the utilization of a Fabry–Perot laser diode (FP-LD) in the proposed structure, a dual-loop OEO with different dual-frequency configurations (which could be tuned up to 12 and 18 GHz) was obtained.

Experimental demonstration of a chaotic communication system with a switchable chaotic carrier wavelength based on two weak-resonant-cavity Fabry–Perot laser diodes

Based on two weak-resonant-cavity Fabry–Perot laser diodes (WRC-FPLDs) with almost identical mode intervals, we propose and demonstrate experimentally, a chaotic communication system with switchable chaotic carrier wavelength. In such a scheme, a WRC-FPLD (called T-WRC-FPLD) subject to filtered feedback provided by a tunable optical filter (TOF) is taken as the transmitter, and the other WRC-FPLD (called R-WRC-FPLD) under optical injection from the T-WRC-FPLD is taken as the receiver. Through setting the central wavelength of the TOF and selecting the matched feedback strength, a desired mode in the T-WRC-FPLD can be chosen to stimulate and output a chaotic signal, whose central wavelength is determined by the central wavelength of the TOF. Thus, the T-WRC-FPLD under filtered feedback can provide a chaotic carrier with a switchable central wavelength. The chaotic signal output from the T-WRC-FPLD is sent to the R-WRC-FPLD and drives the R-WRC-FPLD for generating a chaotic signal. Under proper injection strength, high-quality chaotic synchronization between the T-WRC-FPLD and R-WRC-FPLD can be realized, and therefore the chaotic communication with switchable carrier wavelength can be implemented in this system. We adopt three different chaotic signals provided by three different modes in the T-WRC-FPLD as the chaotic carriers, respectively, and inspect the performances of the system. The experimental results show that, for the three cases, all the correlation coefficients between the T-WRC-FPLD and R-WRC-FPLD can be larger than 0.94 under optimized operating parameters. Via the high-quality chaotic synchronization between the T-WRC-FPLD and R-WRC-FPLD, a 5 Gb/s message encrypted in each chaotic carrier can be successfully decrypted at the receiver for the three cases, and the bit error ratios are all lower than 3.8 × 1 0 − 3 , which is the hard-decision forward error correction threshold.

Improvement of the signal-to-noise ratio in a low power self-mixing interferometer using a coupled interferometric effect.

We present experimental results of a low-emission self-mixing interferometer that uses a coupled interferometric effect to improve the signal produced by a vibrating target. This method is intended to be useful in applications where the target is prone to be damaged by high-intensity laser sources. The beam of a Fabry-Perot laser diode is split and ∼21% of the original emission is used to measure the harmonic micro-displacements of the target using the self-mixing effect. A portion of the residual beam, which also carries the interferometric information related to the target displacement, is reinjected back into the laser cavity by means of a fixed reflector, causing a second interferometric phenomenon that improves the signal-to-noise ratio of the measurement by up to ∼13 dB. A theoretical description of the phenomena is also proposed. Further, we apply this technique to the two most common self-mixing sensing schemes: internal photodiode and junction voltage. The reported results show good agreement with theory and prove the capability of the method to enhance the SNR in SMI schemes.

Distributed-feedback blue laser diode utilizing a tunnel junction grown by plasma-assisted molecular beam epitaxy

In this paper, we demonstrate a novel approach utilizing tunnel junction (TJ) to realize GaN-based distributed feedback (DFB) laser diodes (LDs). Thanks to the use of the TJ the top metal contact is moved to the side of the ridge and the DFB grating is placed directly on top of the ridge. The high refractive index contrast between air and GaN, together with the high overlap of optical mode with the grating, provides a high coupling coefficient. The demonstrated DFB LD operates at λ=450.15 nm with a side mode suppression ratio higher than 35dB. The results are compared to a standard Fabry-Perot LD.

Simultaneous Generation of Multi-Channel Broadband Chaotic Signals Based on Two Unidirectionally Coupled WRC-FPLDs

We propose and demonstrate experimentally a scheme for simultaneously generating multi-channel broadband chaotic signals based on two unidirectionally coupled weak-resonant-cavity Fabry-Perot laser diodes (WRC-FPLDs) with almost the same mode interval, where one WRC-FPLD is utilized as master WRC-FPLD (M-WRC-FPLD) and the other is used as slave WRC-FPLD (S-WRC-FPLD). Under the optical injection from the M-WRC-FPLD with suitable injection parameters, multiple longitudinal modes of the S-WRC-FPLD can be simultaneously driven into chaotic states, which can provide multi-channel chaotic signals. Via a tunable optical filter, we inspect the performances of 9-channel chaotic signals, the results show that the chaotic bandwidths are within the range of 8∼15 GHz for all the 9-channel chaotic signals. Furthermore, the influences of the injection power and frequency detuning on the performances of the chaotic output from one of the channels are also analyzed.

Technologies for future wavelength division multiplexing passive optical networks

This study reviews key technologies of next generation wavelength division multiplexing passive optical networks (WDM-PONs). The authors have studied WDM-PONs with centralised lightwave source and direct detection, where a wavelength-reuse system is employed to transmit the uplink data by using a colourless transmitter at the optical network unit (ONU). WDM-PON system was demonstrated using a Fabry-Perot laser diode as a colourless transmitter at the ONU for differential phase-shift keying (DPSK) downlink signals and on-off keying uplink signals. The constant-amplitude feature of the DPSK modulation could retain a great extinction ratio of the downlink signal and decrease the noise to the uplink signal. The proposed scheme offers a promising solution for future PONs.

Data erasure in Fabry–Perot Diode Lasers: effects of facet reflectivity

ABSTRACTIn this study, the effects of facet reflectivity on the data erasure ability of injection-locked Fabry Perot Laser Diode (FPLD), based on a remodulation method in wavelength division multiplexed passive optical network (WDM PON), were investigated. For this purpose, the feasible front facet reflectivity of FPLD was determined as between 0.2% and 7%, depending on the specified injected power interval. Firstly, the system carried out analysis without applying data at the user end to comprehensively demonstrate how much downstream data was completely erased in FPLD. Then, 2.5 Gb/s of non-return-to-zero (NRZ) data was applied and the results compared with the erased downstream signal without data. The results show that upstream transmission improved with an increase in facet reflectivity between 0.2% and 7%.

A perfect secure optical-network with an anti-correlated noise

We propose a perfect secrecy optical communication with an anti-correlated noise between wavelength-division-multiplexed (WDM) channels. The anti-correlated noise carries confidential information. By sending the different WDM channels to different communication paths in optical communication networks (wired and/or wireless), the achievable signal-to-noise ratio for eavesdroppers can be restricted to much less than that of a target receiver. We demonstrate a perfect secrecy optical network with a three-channel anti-correlated noise generated by using a Fabry–Perot laser diode and a broadband light source. The secure data-rate of 3.95-Gb/s was achieved against an eavesdropper on a single path. We also investigate a secrecy capacity as a function of the number of eavesdropped paths. Finally, security enhancement methods for the proposed system are introduced.

Suppression of parasitic lasing and inter-pulse self-pulsing in a pulsed Erbium–Ytterbium co-doped fiber amplifier

Performance of an Erbium–Ytterbium co-doped fiber (Nufern PM EYDF 12/130) has been investigated as a power amplifier stage for developing a pulsed, high peak power, 1550 nm laser with 30 ns pulse duration at 10 kHz repetition rate. A directly modulated, broadband, Fabry–Perot laser diode has been employed as seed laser in all fiber master oscillator power amplifier (MOPA) configuration. Amplifier performance was significantly improved by improving the spectral quality of seed and preamplifiers using two band-pass filters in tandem. This may be attributed to the reduction in inter-pulse Amplified Spontaneous Emission (ASE) noise. Comparative results have been presented for two different MOPA configurations. MOPA with broader signal spectrum resulted in Yb parasitic lasing at 5 W pump power causing roll over in the output energy. Also, onset of strong self-pulsing was observed during off period (in absence of signal pulse) at ~ 6.3 W input. Nature of these pulses resembled relaxation oscillations. Theoretically calculated time period (10–12 µs) of the self-pulses at various pump powers matched fairly well with the experimental results. However, with improved signal spectral quality, no such inter-pulse self-pulsing and parasitic lasing was observed up to 12 W pump power. More than 75 µJ energy per pulse was achieved, limited by power-handling capability of the output isolator. We present here several novel experimental results in terms of spectral, temporal and energy output for a pulsed EYDF amplifier generating 2.5 kW pulses @ 1550 nm.

Data erasure analysis of FPLD based on remodulation bidirectional PON system

ABSTRACTThe data-erasing mechanism is a promising cost-efficient option for future broadband access networks. This paper analyzes the data erasure efficiency of the Fabry Perot Laser Diode(FPLD) at a speed of 5 Gb/s based on bidirectional wavelength division multiplexed passive optical networks (WDM PONs) using the carrier remodulation technique. The effects of many parameters such as the biasing current, extinction ratio, confinement factor, and injection power demonstrate the data erasure efficiency of the FPLD in the upstream bidirectional remodulation PON system are discussed. The novelty of this study is the very high front facet reflectance results are demonstrated. A range of injection power from −25 dBm to 0 dBm and an FPLD bias current of 20-100 mA were applied to the system. The injection power below 0 dBm and bias current above 30 mA provide successful transmission of upstream data. The FPLD can suppress the residual downstream extinction ratio <0.5 dB.

Writing 10 Gb/s Data Bits With Addressing Using External Cavity-Based SMFP-LDs

Memory accessing is one of the challenging issues for utilizing the improvements in processor speed. Due to the rapid enhancement on processor speed compared to the memory accessing technique, the gap between the memory accessing and processor speed is rapidly widening. Hence, a new technique to address this issue needs to be devised. In this paper, we experimentally demonstrate the complete scheme of wavelength division multiplexing enabled memory write operation in the desired memory location using single mode Fabry–Perot laser diodes (SMFP-LDs). For a proof of concept, we demonstrate writing a stream of data bits at 10 Gb/s data rate in a memory unit that consists of four single bit set–reset (SR) latches with a unique address. The input data bits are stored in the respective latch of the memory bank in accordance with the address bit set along with a write instruction. A higher order of memory units with address decoding can be realized by increasing the higher order of decoder and the memory units. The observed optical domain waveforms at the respective nodes of each block, eye diagram, SNR, and bit error rate (BER) prove the verification of writing input data to the desired memory locations using SMFP-LDs. We observed an extinction ratio of more than 12 dB, no noise floor at the BER of 10−12, and a maximum power penalty of about 2.5 dB in the proposed scheme.

QAM Transmission over RoF Using Fabry Perot Laser Diode and Continuous Wave Laser Diode

This paper introduces the Quadrature Amplitude Modulation (QAM) Radio over Fiber (RoF) framework dependent on Optical Frequency Comb (OFC) generation utilizing Fabry-Perot Laser Diode (FPLD) and Continuous Wave Laser Diode (CWLD). In this, optical Millimeter-Wave (MMW) can be created ether utilizing ease FPLD with an outside optical infusion or a continuous wave laser diode. At the base, optical MMW can be recognized by utilizing photodetector in the two transmissions. The experimental results are explained by using the constellation and eye diagram.

Modulation amplitude dependence of optical modulation distortion in IM-DD communication

In this paper, the authors have studied the modulation amplitude dependence of optical modulation distortion when the Fabry-Perot laser diode (FPLD) is bias current modulated by a sinusoidal signal. The fundamental modulating signal can be, in general, accompanied by other harmonics. The second and third harmonic modulation distortion along with the total harmonic modulation distortion have been calculated theoretically and measured experimentally. The difference between theory and experiment has also been explained.

Self-injection locking efficiency of a UV Fabry-Perot laser diode.

In this Letter, we have studied the performance of a gallium nitride 370nm Fabry-Perot laser diode self-injection locked via a high quality (Q-) factor magnesium fluoride whispering gallery mode (WGM) resonator and show that the state of locking strongly depends on frequency detuning between the internal laser cavity and the resonator modes. Optimizing the detuning, we were able to observe monochromatic laser emission with a sub-100kHz linewidth. The Q-factor of the resonator measured in this regime exceeded 109.

Radio Over Fiber-Based Wavelength Division Multiplexed/Time Division Multiplexed Passive Optical Network Architecture Employing Mutual Injection Locked Fabry-Perot Laser Diodes

Abstract We demonstrate a radio-over-fiber-based hybrid wavelength-division-multiplexed/time division multiplexed passive optical network (PON) to transmit 5 Gbps data rate to serve 32 subscribers. A broadband light source (BLS) is realized by mutual injection locking between two Fabry-Perot laser diodes at the transmission section to seed wavelength-division-multiplexed channels. Mutual injection locking technique is used to enhance the performance over single Fabry-Perot laser diode and 15 dB/Hz improvements in relative intensity noise(RIN) is realized in our proposed network system. All-optical up-conversion of a 10-GHz 1.25 Gbps on off keying radio frequency (RF) signal is achieved using one single-arm Mach-Zehnder modulator (MZM). Transmission performance over 25-km single mode fiber is investigated. Low bit error rate with enhanced eye-diagram is obtained in our proposed system. As a result, the radio over fiber (ROF)-based wavelength-division-multiplexed/time division multiplexed PON set up employing mutually injection locked Fabry-Perot laser diodes can be a better choice in high speed long-haul optical communication system.

Confocal flowmeter based on self-mixing interferometry for real-time velocity profiling of turbid liquids flowing in microcapillaries.

We propose a new confocal device for flow profiling in microcapillaries. A viewfinder system is developed using a visible light microscope, allowing focusing with high precision an 830 nm Fabry-Perot laser diode on a microchannel. By means of a novel confocal approach, the Doppler shift produced by the particles of a turbid liquid moving in the focal plane can be measured in real time using the well-known self-mixing effect. The resolution of this device is characterized in function of the full width at half maximum of the Gaussian frequency peak related to the self-mixing signal in the frequency domain. Velocity measurements for flow rates from 0.2 to 1.6 mL/min are presented, and the results demonstrate that the method reduces the phase noise and the effects of the out-of-focus particles, allowing straightforward flow profiling in microchannel structures.