Abstract
In this paper, a simple image rejection mixer based on the dispersion effect in the single mode fiber is proposed and experimentally demonstrated for the radio-over-fiber (RoF) system. The key idea is to control the DC bias voltages of the dual parallel Mach-Zehnder modulator (DPMZM) to compensate for the desired components and eliminate the image induced components simultaneously during the fiber transmission. The experimental results show, the image rejection ratio (IRR) of ∼50 dB is realized, and the spurious free dynamic range (SFDR) is about 100.75 dB·Hz2/3. In addition, the results also demonstrate an image-free intermediate frequency (IF) range of 0.5 GHz–9.5 GHz. This image-free mixer can be widely employed in the radio-over-fiber (RoF) system, and greatly simplify the receiver structure in the base station.
Highlights
For many RF systems, the frequency mixer is a significant device that converts the high frequency to a lower one or converts the low frequency to a higher one, so that the signal processing can be implemented in different occasions [1]
With the development of the communication system, the photonic mixers that implemented through a heterodyne structure to obtain a nonzero intermediate frequency (IF) signal will be influenced by image signals [7], [8].The image signal, which is defined as fI M = fL O − fI F and usually generated by human sources
In order to verify the feasibility of the proposed image rejection method shown in Fig. 1, a simulation is firstly performed through commercial software of Optisystem 7.0
Summary
For many RF systems, the frequency mixer is a significant device that converts the high frequency to a lower one or converts the low frequency to a higher one, so that the signal processing can be implemented in different occasions [1]. Extra devices are required in these mixers such as phase shifter [12]–[15], 90° electrical hybrid coupler [16]–[18] or 90° optical hybrid coupler [19]–[21] to satisfy the phase cancellation condition. For these methods, the phase accuracy is greatly needed to guarantee the phase cancellation condition. These excellent performed image rejection mixers often concentrate on the signal high quality receiving, but pay less attention to efficient transmitting
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