Transmission of Wireless MIMO-Type Signals Over a Single Optical Fiber Without WDM

Abstract

The problem of sending multiple wireless signals of the same carrier frequency, such as the multiple-input-multiple-output (MIMO) signals specified in the IEEE 802.11n standard, over a single optical fiber is that they overlap in the frequency domain. Traditional solutions using wavelength division multiplexing or even deploying multiple optical fibers are, however, far too expensive for this particular application. We propose and demonstrate transmission of three MIMO radio signals all with a 11-MSymb/s, 16 quadrature amplitude modulation, and 2.44-GHz carrier frequency over an optical fiber using a novel single-sideband frequency-translation technique. The maximum crosstalk level between the different MIMO channels was . Compared with sub-carrier multiplexing, where transmitting three such signals would require frequency shifting two of them using two separate local oscillators (LOs), the new technique requires only a single low-frequency LO. This novel technique can be implemented in add-on modules to work with existing commercially available radio-over-fiber systems, which were not originally designed to carry such MIMO signals having the same frequency.