All‐optical correlator based on modal dispersion in multimode fiber

Abstract. Weproposeanddemonstrateanall-opticalcorrelatorbasedonmodaldispersioninamultimodefiber.Many of the modes can be excited in a large core high numerical aperture step-index multimode fiber underoverfilled launching. The incident optical signal is copied into different modes and a time delay is introducedby the modal dispersion. We use a mask with slits as a space filter to select the modes needed. A correlatorof the mask and input signal is achieved at the output end. Thanks to the use of modal dispersion, the correlatorisnearlyindependentofthewavelengthandbandwidthoftheinputsignal.Byadjustingtheslitsonthemask,thetarget patterns of the correlator can be changed easily. A radio frequency signal detection is also experimentallydemonstrated with this construction. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE) [DOI: 10.1117/1.OE.55.3.031119] Keywords: multimode fiber; all-optical correlator; optical signal processing; radio frequency signal detection.Paper 151116SS received Aug. 13, 2015; accepted for publication Nov. 3, 2015; published online Dec. 8, 2015.