A Method for Testing Chirp Parameters of Electro-optic Intensity Modulator Based on Phase Comparison

Abstract

A method for testing the chirp parameters of electro-optic intensity modulators based on phase comparison, aiming to provide a test method that can meet the needs of broadband and high-precision chirp parameters for electro-optic modulators, and at the same time avoid the problem of calibration of electro-optic detectors in experiments , and use the frequency-shifting heterodyne structure to realize the low-frequency test method of the chirp parameters of the electro-optic modulator, avoiding the use of photodetectors with high-frequency bandwidth. The optical carrier input to the frequency-shifting heterodyne structure is divided into two, the optical carrier of the upper arm is modulated by the electro-optical modulator to be tested, the optical carrier of the lower arm is frequency-shifted and modulated by the auxiliary phase modulator, and the two optical signals are captured by the photodetector. The frequency is converted into an electrical signal, and the electrical signal of a specific frequency is filtered out through a fixed electrical filter, and finally the time domain waveform of the electrical signal is obtained through an oscilloscope; by twice adjusting the bias voltage of the electro-optic intensity modulator to be tested, the specific frequency is observed The phase difference of the electrical signal, calculate the phase difference to obtain the chirp parameter of the electro-optic intensity modulator; change the frequency of the radio frequency signal loaded on the modulator to be tested, repeat the above process, and it can be measured that the electro-optic intensity modulator under test is at different modulation frequencies The chirp parameter of .

Description

technical field [0001] The invention relates to the technical field of microwave photonics, in particular to a method for measuring chirp parameters of an electro-optical intensity modulator. Background technique [0002] With the development trend of high-speed, wide-band and long-distance transmission in optical fiber communication systems, electro-optic intensity modulators have become one of the key components of high-speed optical fiber communication systems. Due to the asymmetry of the waveguide structure and the different driving voltage losses of the upper and lower arms of the traditional Mach-Zehnder waveguide structure electro-optical intensity modulator, a chirp closely related to the fiber dispersion and the optical fiber intensity modulator is formed during the intensity modulation process. The chirp parameter has become an important factor limiting high-speed long-distance transmission. Therefore, in order to improve the overall transmission performance of the...

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Problems solved by technology

[0003] At present, the methods for measuring the chirp parameters of electro-optical intensity modulators with Mach-Zehnder structures are roughly divided into electrical domain measurement methods and optical domain measurement methods. The typical representative of optical domain measurement methods is spectral analysis (Y Q Shi, L S Yan, A EWillner. High-speed electro-optic modulator characterization using opticspectrum analysis.Journal of Lightwave Technology.2003,21(10):2358-23:NCourjal and J M Dudiley.Extinction-ratio-independent method for chirpmeasurements of Mach-Zehnder0ptics.Express modulators 2004,12(3):442-448.), this method utilizes the optical carrier in the spectrum and the power ratio of the sideband to obtain the chirp parameter of the electro-optic intensity modulator, but is limited by the resolution of the wavelength of the commercial spectrum analyzer ( 0.01nm) limitation and the influence of the laser line width, it is impossible to accurately measure the chirp parameters in the low frequency range; the electrical domain measurement method includes the optical frequency discrimination method (J Provost and F Grillot. Measuring the Chirp and the Linewidth Enhancement Factor of Optoelectronic Devices with a Mach-Zehnder Interferometer.IEEE Photonics Journal.2011,3(3):476-488:J SBakos,G P Djotyan,P N.Ignacz,el al.Generation of frequency-chirped laserpulses by an electro-optic amplitude modulator. Optics and Lasers in Engineering.2009,47(1):19-23.), heterodyne method (E Rogersj, J L Carini, J A Pechkis, elal.Characterization and compensation of the residual chirp in a Mach-Zehnder-type electro-optical intensity modulator. Optics Express. 201 0,18(2):1166-1176; D J Krause and J C Cartledge.Technique for Measuring the Optical PhaseTransfer Function.IEEE Photonics Journal.2004,16⑶:1915-1917.), fiber optic transmission method (FDevaux, Y Sorel and J F Kerdiles .Simple measurement of fiber dispersion and ofchirp parameter of intensity modulated light emitter.Journal of LightwaveTechnology.1993,11(12):1937-1940.), wherein the optical frequency discrimination method uses the interferometer method to convert the amplitude-frequency and phase of the device under test The frequency response is extracted to measure chirp parameters, but the interferometer is greatly affected by temperature, and has high requirements on the bandwidth and resolution of the free spectral range (FSR) of the interferometer, and the adjustment is complicated; the heterodyne method uses Optical heterodyne technology measures the ratio of the phase and amplitude information of the modulator to directly obtain the chirp parameters, but is affected by the stability of the laser and is limited to low-bandwidth time-domain measurements; the optical fiber transmission method uses the intensity-modulated optical signal in the dispersion fiber Propagation characteristics, easily affected by fiber length and environment

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