Compact Three-Dimensional Polymer Waveguide Mode Multiplexer

Abstract

We propose a compact three-dimensional waveguide mode (de)multiplexer based on the configuration of two collocated asymmetrical directional couplers, formed with two dissimilar single-mode cores placed alongside a central rectangular threemode core in the horizontal and vertical directions, respectively. The waveguides are designed to allow the LP 11a and LP 11b modes of the central core to completely couple to the LP 01 modes of the two side cores, respectively, with the LP 01 mode staying in the central core, which is tapered down at one end to strip off any remaining LP 11 modes. We fabricate the device with polymer materials by the conventional microfabrication process. A typical fabricated device, which has a total length of 9.0 mm, shows coupling ratios varying from 91% to 99% for the two LP 11 modes, and crosstalks among the modes in the side cores varying from −23.2 to −14.6 dB in the wavelength range 1530-1570 nm (the C-band). The crosstalks in the central core are negligible. The insertion loss of the device with fiber leads is about 10 dB and the mode-dependent loss is about ±1 dB. The performance of the device is weakly sensitive to the polarization state of light and insensitive to temperature variations. This device can be used in broadband mode-divisionmultiplexing transmission systems based on few-mode fibers.Index Terms-Integrated optics, multiplexing, optical planar waveguide coupler, optical polymer, optical waveguide component.

Opto-Electronics Review

“…Operation principle of the mode coupling converters is based on the coupling between the fundamental and the selected high-order mode under the condition of their phase matching. Such a mode coupling is usually achieved by using ADC, [44][45][46][47][48][49][50][51][52][53][54][55][56][57]73,78], ring [58,59], LPG [60][61][62][63][64][65]72,74,75], BG [66,67], dielectric metasurface structure [68][69][70], and grating-assisted coupler [71], and so on. Their key performances have been summarized in Table 2 in the Appendix.…”

“…Their experimental mode converter shows the MCEs from 53% to 68% and 80% to 99%, and the MERs from 26 dB to 32 dB and from 35 dB to 37 dB for the LP01-LP11a and LP01-LP11b conversions, respectively, both with an IL lower than ~1 dB over 1500-1580 nm. Subsequently in 2015 J. L. Dong et al [50] also proposed a similar 3D waveguide mode multiplexer formed with horizontal and vertical ADCs to achieve the LP01-LP11a and LP01-LP11b conversions. Their proposed device consists of two dissimilar single-mode core waveguides placed along with a central three-mode rectangular waveguide in the horizontal and vertical direction, respectively.…”

Selective Mode Excitation: A Technique for Advanced Fiber Systems

“…Those units are based on selective mode couplers which excite/detect independently fiber modes of different orders. A set of such elements basing on different operating principles have been developed (for example, [4][5][6][7][8][9][10][11][12][13][14][15][16]). In most cases, selective excitation of fiber modes is performed with external units that are built as waveguide (fiber or integrated optical) elements or bulk devices based on traditional optical elements.…”

Design and fabrication of three-dimensional polymer mode multiplexer based on asymmetric waveguide couplers

“…Though a specific designed mode rotator can be applied to overcome this obstacle, it increases the complexity in design and fabrication [37]. Three-dimensional waveguide MUX/DEMUX with coupling in both horizontal and vertical direction then becomes a reasonable option [38][39][40]. Besides, conventional microfabrication technologies of spin-coating and photolithography can be adopted in the fabrication.…”

“…Besides, conventional microfabrication technologies of spin-coating and photolithography can be adopted in the fabrication. While the distance between two output ports of the upper and lower waveguide of a vertical parallel waveguide coupler is so small that an angled transitional waveguide is essential to separate two output ports [38,39]. Then, there will be errors in coupling ratio calculations if the mode-coupling within the transitional region was not considered.…”