Research On The High-performance Optical Modulator Using A Twin-core Fiber

All optical networks is a hot researching field of communication, it commits to transmit optical signal transparently across the communication network without going through any OEO conversion. To achieve the purpose of this kind of optical signal transmission, it is essential to develop all-optical devices which can transmit optical signal transparently. Twin-core fiber is special fiber that has two cores. when the distance of these two cores is small, the coupling occurs between these two cores, which lead to the exchanging of power periodically between these two cores. as increasing of the distance of the two cores, optical signals coupling between the inner cores will become weaker. the two cores will not couple when their distance is big ennough. If the air is filled tetween these two cores, the ability of bounding optical signal of the optical fiber cladding will enhance, which results that the exchanging of optical power in the fiber will not accur. Based on these features, we can design two kinds of optical modulator, coupling modulator and M-Z modulator.The couple modulator is based on the coupling character of TCF. When pasting a section of the piezoelectric ceramic, the length and the the refractive index of TCF will be changed by changing the length of the piezoelectric ceramic. As a result,the output of the optical power of TCF will be changed, and the purpose of modulating optical is realized. We analyze several performance parameters of this modulation in this article, the analysis results show that the insertion loss of the modulator can be achieved1dB or less in the situation of good splicing beteen the twin-core fiber and single mode fiber; the extinction ratio can be achieved more than20dB; their half-wave voltage is10V or less; the bandwidth which depends on the frequency response of PZT can reach1GHz or above. We also design the preliminary experiment to verify the modulator’s output and get the result of simulation, and the result shows that when modulating the Gaussian pulse signal, the signal waveform deviation is small, about2.5%.The MZ modulator based on TCF is filled air in the middle part of TCF between the two cores, and the middle part of TCF will not couple and the other part will still couple. When pasting the piezoelectric ceramic to the core1side of TCF, the length and the refractive index of core1will changed with the change of the piezoelectric ceramic’s length, while the the length and the refractive index of core2is not change approximatly, and the phase difference of two cores appears, then the whole TCF can be regard as M-Z interferometer modulator. We analyze several performance parameters of this modulation in this article, the analysis results show that the insertion loss of the modulator is similar with the TCF couple modulator and it can be achieved1dB or less in the situation of good splicing beteen the twin-core fiber and single mode fiber; it has better bandwidth characters; the extinction ratio is easier to be achieved more than20dB than the TCF couple modulator; their half-wave voltage is1V or less. We also design the preliminary experiment to verify the modulator’s output and get the result of simulation, and the result shows that when modulating the sin signal, the signal waveform deviation is small, about3.2%.