[1] [1] Mohammed W S, Mehta A, Johnson E G. Wavelength tunable fiber lens based on multimode interference [J]. Lightwave Technology, 2004, 22: 469-477.

[2] [2] Hofmmnn Peter, Mafi Arash, Jollivet Clemence, et al. Detailed investigation of mode-field adapters utilizing multimode-interference in graded index fibers [J]. Journal of Lightwave Technology, 2012, 30: 2289-2297.

[5] [5] Dhawan Anuj, Muth J F. In-line fiber optic structures for environmental sensing applications [J]. Optics Letters, 2006, 31: 1391-1393.

[6] [6] Saurabh Mani Tripathi. Strain and temperature sensing characteristics of ingle-mode-multimode-single-modeStructures [J]. Journal of Lightwave Technology, 2009, 27: 2348-2356.

[7] [7] Lorenser D, Yang X, Sampson D D. Accurate modeling and design of graded-index fiber probes for optical coherence tomography using the beam propagation method [J].IEEE Photonics Journal, 2013, 5.