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1.
Opt Express ; 27(12): 16791-16797, 2019 Jun 10.
Article in English | MEDLINE | ID: mdl-31252899

ABSTRACT

We report on the direct intensity modulation characteristics of a high-speed resonant tunneling diode-photodetector (RTD-PD) with an oscillation frequency of 79 GHz. This work demonstrates both electrical and optical modulation and shows that RTD-PD oscillators can be utilized as versatile optoelectronic/radio interfaces. This is the first demonstration of optical modulation of an RF carrier using integrated RTD-PD oscillators at microwave frequencies.

2.
Appl Opt ; 56(4): 1079-1086, 2017 Feb 01.
Article in English | MEDLINE | ID: mdl-28158115

ABSTRACT

In this paper, we have experimentally investigated the optimized bias current of semiconductor optical amplifiers (SOAs) to achieve high-speed input pulse train amplification with high gain and low distortion. Variations of the amplified output pulse duration with the amplifier bias currents have been analyzed and, compared to the input pulse duration, the amplified output pulse duration is broadened. As the SOA bias current decreases from the high level (larger than the saturated bias current) to the low level, the broadened pulse duration of the amplified output pulse initially decreases slowly and then rapidly. Based on the analysis, an optimized bias current of SOA for high-speed pulse train amplification is introduced. The relation between the SOA optimized bias current and the parameters of the input pulse train (pulse duration, power, and repetition rate) are experimentally studied. It is found that the larger the input pulse duration, the lower the input pulse power or a higher repetition rate can lead to a larger SOA optimized bias current, which corresponds to a larger optimized SOA gain. The effects of assist light injection and different amplifier temperatures on the SOA optimized bias current are studied and it is found that assist light injection can effectively increase the SOA optimized bias current while SOA has a lower optimized bias current at the temperature 20°C than that at other temperatures.

3.
Opt Express ; 24(23): 26838-26850, 2016 Nov 14.
Article in English | MEDLINE | ID: mdl-27857412

ABSTRACT

Indoor visible light communications (VLC) combines illumination and communication by utilizing the high-modulation-speed of LEDs. VLC is anticipated to be complementary to radio frequency communications and an important part of next generation heterogeneous networks. In order to make the maximum use of VLC technology in a networking environment, we need to expand existing research from studies of traditional point-to-point links to encompass scheduling and resource allocation related to multi-user scenarios. This work aims to maximize the downlink throughput of an indoor VLC network, while taking both user fairness and time latency into consideration. Inter-user interference is eliminated by appropriately allocating LEDs to users with the aid of graph theory. A three-term priority factor model is derived and is shown to improve the throughput performance of the network scheduling scheme over those previously reported. Simulations of VLC downlink scheduling have been performed under proportional fairness scheduling principles where our newly formulated priority factor model has been applied. The downlink throughput is improved by 19.6% compared to previous two-term priority models, while achieving similar fairness and latency performance. When the number of users grows larger, the three-term priority model indicates an improvement in Fairness performance compared to two-term priority model scheduling.

4.
Opt Lett ; 37(3): 344-6, 2012 Feb 01.
Article in English | MEDLINE | ID: mdl-22297347

ABSTRACT

High output power 40 GHz 1.55 µm passively mode-locked surface-etched distributed Bragg reflector (DBR) lasers with monolithically integrated semiconductor optical amplifiers are reported. These are based on an optimized AlGaInAs/InP epitaxial structure with a three quantum well active layer and an optical trap layer. The device produces near transform limited Gaussian pulses with a pulse duration of 3.3 ps. An average output power during mode-locked operation of 130 mW was achieved with a corresponding peak power of >1 W.

5.
Opt Express ; 20(3): 3268-74, 2012 Jan 30.
Article in English | MEDLINE | ID: mdl-22330565

ABSTRACT

Optical self seeding feedback techniques can be used to improve the noise characteristics of passively mode-locked laser diodes. External cavities such as fiber optic cables can increase the memory of the phase and subsequently improve the timing jitter. In this work, an improved optical feedback architecture is proposed using an optical fiber loop delay as a cavity extension of the mode-locked laser. We investigate the effect of the noise reduction as a function of the loop length and feedback power. The well known composite cavity technique is also implemented for suppressing supermode noise artifacts presented due to harmonic mode locking effects. Using this method, we achieve a record low radio frequency linewidth of 192 Hz for any high frequency (>1 GHz) passively mode-locked laser to date (to the best of the authors' knowledge), making it promising for the development of high frequency optoelectronic oscillators.


Subject(s)
Amplifiers, Electronic , Electronics/instrumentation , Lasers, Semiconductor , Oscillometry/instrumentation , Computer-Aided Design , Equipment Design , Equipment Failure Analysis , Feedback
6.
Opt Express ; 19(10): 9737-43, 2011 May 09.
Article in English | MEDLINE | ID: mdl-21643230

ABSTRACT

We measured the absorption recovery times in reverse biased AlInGaAs multiple quantum well material designed to emit at around 1.5 µm wavelength. Absorption recovery times as low as 2.5 ps were found at -4V bias, with values below 5 ps consistently found for biases above 3 V. The short absorption recovery times obtained under reverse bias were confirmed by using cross-absorption modulation in the material to demonstrate wavelength conversion of a 10 GHz pulse train, showing both up and down conversion of the incident pulses.

7.
IEEE Photonics Technol Lett ; 23(16): 1148-1150, 2011 Aug 15.
Article in English | MEDLINE | ID: mdl-23814452

ABSTRACT

We propose and demonstrate a simple and stable low-phase noise optoelectronic oscillator (OEO) that uses a laser diode, an optical fiber delay line and a resonant tunneling diode (RTD) free-running oscillator that is monolithic integrated with a waveguide photo-detector. The RTD-OEO exhibits single-side band phase noise power below -100 dBc/Hz with more than 30 dB noise suppression at 10 kHz from the center free-running frequency for fiber loop lengths around 1.2 km. The oscillator power consumption is below 0.55 W, and can be controlled either by the injected optical power or the fiber delay line. The RTD-OEO stability is achieved without using other high-speed optical/optoelectronic components and amplification.

8.
Opt Express ; 14(15): 6858-63, 2006 Jul 24.
Article in English | MEDLINE | ID: mdl-19516868

ABSTRACT

This paper discusses the effect of slow-light in Vertical-Cavity Semiconductor Optical Amplifiers. A Fabry-Perot model is used to predict the group delay (GD) and GD-bandwidth performance of a VCSOA operated in reflection in the linear regime. It is shown that the GD depends on all cavity parameters while the GDxGD-bandwidth product only depends on the gain. Experimental demonstration with a 1300nm GaInNAs VCSOA is used to validate the model and demonstrate tunable GDs between 25 and 100 ps by varying the VCSOA gain. Experimental distortion of the signals induced by nonlinear effects is also presented.

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