Influence of Fiber Properties on Harmonic and Intermodulation Distortions of Semiconductor Lasers

This paper introduces modeling and simulation of the harmonic and intermodulation distortions of semiconductor laser radiating an optical fiber link. The study is based on the rate equation model of semiconductor lasers excited by injection current with two sinusoidal tones separated by a radio frequency. The modulated laser signal is modeled in both the time and frequency domains. The laser signal distortions include the 2nd and 3rd harmonic distortion (2HD and 3HD), and the third-order intermodulation distortion IMD3. The laser is assumed to be modulated around its relaxation frequency. Influence of the modulation depth on the signal distortion is investigated when the laser is free running and when it is radiating a fiber link. In the latter case, influences of the attenuation and chromatic dispersion on the signal dispersion are elucidated when the fiber length increases up to 10 km. The results show that the fiber attenuation does not affect the signal distortion, whereas the chromatic dispersion affects both the harmonic distortions and intermodulation distortion. Sending the laser signal down an optical fiber of length ~ 5km can help in minimizing 2HD which is the dominant harmonic distortion of the modulated signal. This range of optical fiber is also characterized with intermodulation distortion less than 0dBc.

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Shaping Lightwaves in Time and Frequency for Optical Fiber Communication

10.21203/rs.3.rs-452651/v1 ◽

2021 ◽

Author(s):

Junho Cho ◽

Xi Chen ◽

Greg Raybon ◽

Di Che ◽

Ellsworth Burrows ◽

...

Keyword(s):

Optical Fiber ◽

Chromatic Dispersion ◽

Kerr Nonlinearity ◽

Optical Fiber Communication ◽

Fiber Communication ◽

Wavelength Division ◽

Wavelength Division Multiplexed ◽

Fiber Link ◽

The Impact ◽

Low Dispersion

Abstract In optical communications, sphere shaping is used to limit the energy of lightwaves to within a certain value over a period. This minimizes the energy required to contain information, allowing the rate of information transmission to approach the theoretical limit if the transmission medium is linear. In optical fiber, however, the sphere shaping induces Kerr nonlinearity in a peculiar way that makes analysis of transmission performance difficult, potentially lowering the communications capacity. In this article, we show how the impact of sphere shaping on Kerr nonlinearity varies with the chromatic dispersion and the structure of shaped lightwaves in time and frequency, and give insights into why the structure matters. As a practical consequence, by optimally controlling the structure of lightwaves in time and frequency, it is experimentally demonstrated that the information rate can be increased by up to 25% in low-dispersion channels on a 2824-km dispersion-managed wavelength-division multiplexed optical fiber link.

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Two wavelength frequency transfer over an optical fiber link

EPJ Web of Conferences ◽

10.1051/epjconf/202023806020 ◽

2020 ◽

Vol 238 ◽

pp. 06020

Author(s):

Carlos Pires ◽

Manuel Abreu ◽

Isabel Godinho ◽

Rui Agostinho

Keyword(s):

Optical Fiber ◽

Fiber Optic ◽

Chromatic Dispersion ◽

Experimental Setup ◽

Standard Frequency ◽

Phase Variations ◽

Fiber Link ◽

Frequency Transfer ◽

Propagation Media

In this paper we present the theory and the experimental setup used to transfer a standard frequency, to synchronize two clocks linked by an optical fiber. In order to verify the accuracy on frequency transfer over fiber link, we prepared an experiment that allows testing the performance of the setup for a variable set of environmental conditions, namely associated to temperature and vibration variations. The experimental setup shows the fiber optic link between one laboratory, where the standard frequency is generated, and another laboratory, where the equipment for simulating temperatures and vibrations are installed. The standard frequency, traceable to UTC(IPQ), is used to modulate two lasers with different wavelength,, injected in the optical fiber. At the end of the optical fiber the signals will be out of phase due to the inherent chromatic dispersion, which is also dependent on the temperature of the propagation media. Measuring the phase variations, caused by temperature gradients in the fiber, we can compensate the frequency transfer and synchronize the clocks. Evaluating all uncertainty components in this model, allows the metrological characterization of the synchronization and obtain the associated uncertainty of this quantity.

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