Conference Paper

19x10-GHz electro-optic ultra-flat frequency comb generation only using single conventional Mach-Zehnder modulator

National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei-shi, Tokyo 184-8795, Japan
DOI: 10.1109/CLEO.2006.4627674 Conference: Lasers and Electro-Optics and 2006 Quantum Electronics and Laser Science Conference. CLEO/QELS 2006. Conference on
Source: IEEE Xplore

ABSTRACT

We demonstrated ultra-flat optical frequency comb generation only using a set of conventional Mach-Zehnder modulator asymmetrically dual-driven by large-amplitude sinusoidal signals with different amplitudes. 19-channel 10-GHz-spaced frequency comb with ≪4.6-dB spectral ripple was experimentally generated.

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    • "Another commonly used comb generation technique entails the use of external optical modulators. This could involve single [11] or multiple external modulators with cascaded [12], nested [13] or loop structures [14]. However, the large insertion loss of the modulator (especially when cascaded) coupled with the modulation efficiency can prove prohibitive. "
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    ABSTRACT: We demonstrate, through experimental results and supporting numerical simulations, the optimum conditions to generate an optical comb via gain switching of a single mode DFB semiconductor laser. The DFB laser is biased appropriately and gain-switched with a large amplitude sinusoidal current, modulating the gain that is sufficient to turn the laser on and off. This results in the generation of a train of short optical pulses albeit with a relatively large amount of temporal jitter. The jitter is as a result of the varying turn on time delay, which breaks the periodicity of the pulses leading to an optical spectrum with no discernible tones. However, we find that the conditions for creating an optical frequency comb exist when the modulation frequency is greater than or equal to the relaxation oscillation frequency of the laser. Corresponding optical pulses are shown to exhibit lower levels of temporal jitter at these optimum points of operation. The spectral purity of the comb tones is analysed, and we show that the FM-noise of the comb tones decreases with increasing modulation frequency with the lower limit set by operating the laser in CW conditions. All of the simulation results were obtained using standard laser rate equations.
    Full-text · Article · Jul 2015 · IEEE Journal of Selected Topics in Quantum Electronics
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    • "). The external injection of the comb source with the ECL improves the SNR of the comb lines, which as previously mentioned, is important for OFDM signals [12]. A wavelength selective switch (WSS) is used to filter two tones separated by 54.3 GHz, Fig. 2 "
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    ABSTRACT: A 25 Gb/s orthogonal frequency division multiplexing (OFDM) 60 GHz radio over fibre transmission system employing an externally injected gain switched DFB laser for millimetre wave generation is demonstrated. The effects of nonlinear distortions, due to a high launch power, on system performance are experimentally investigated. Single sideband (SSB) OFDM is employed to reduce the fibre nonlinearity effects. Keywords—radio over fibre (RoF), gain-switching, optical comb source, orthogonal frequency division
    Full-text · Conference Paper · Oct 2014
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    • "Comb generation with a tunable FSR and tunable central wavelength can be achieved utilising external optical modulators. This system can be implemented using either a single modulator [6] or several cascaded external modulators [7]. However, these systems must overcome the large insertion loss, modulation efficiency and instability due to bias drift associated with the modulators. "
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    ABSTRACT: A single sideband (SSB) sub carrier multiplexed (SCM) quadrature phase shift keyed (QPSK) 60 GHz radio over fibre transmission system employing a gain switched DFB laser for millimetre wave generation is demonstrated. Error free transmission of a 1.25 Gbaud/s QPSK signal over 25 km of standard single mode fibre (SSMF) is achieved with a low cost laser and low cost electronics. Our research demonstrates a cost effective mm-wave generation and transmission system which is baud rate/modulation format scalable.
    Full-text · Conference Paper · Oct 2014
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