Design and Fabrication of Novel Symmetric Low-Loss 1 × 24 Optical Power Splitter

In this paper, a three-branch structure with different output widths, broadening, and transition waveguide are discussed in detail. Based on the three-branch structure, a compact, low-loss, and good uniformity 1 × 24 optical power splitter is designed and fabricated using silica-based PLC technology on quartz substrate. The measurement results show that the insertion loss, the uniformity, wavelength-dependence loss of the splitter are less than 14.8, 0.92, and 0.93 dB, respectively, in the wavelength range from 1.25 to 1.65 μm. The polarization dependence loss is less than 0.16 dB in the wavelength of 1.27, 1.31, 1.49, 1.55, and 1.625 μm.

I. Introduction

Optical power splitters, as a key component of passive optical network of Fiber to the home, are widely used and researched recent years. Optical power splitters are traditionally fabricated by fused biconical taper method as demonstrated in [1]– [3], which are difficult to adjust the splitting ratio and integrate with other optical devices. The dimension becomes larger and larger with the increasing output numbers. The other fabrication method is Ion-exchange technology as mentioned earlier in [4]– [7] , which are widely studied because of its low cost and easy realization. However, the Ion-exchange process is hard to control and increases the fabrication difficulty. Another fabrication method is planar lightwave circuits (PLC) technology. PLC splitters have the advantages of compact size, low loss, and good uniformity. Many 1 or 2 × N (, ) optical power splitters have been reported using this technology as demonstrated in [8]– [14]. Optical power splitter with output branches can be obtained by cascaded . Besides, other special optical power splitters, such as 1 × 3, 1 × 6, 1 × 12, 1 × 24, are desirable in some fields. These special splitters are composed of a three-branch and some Y-branch elements, where the three-branch is different from the Y-branch in structure and difficulty in the uniformity design. Good uniformity is hard to obtain because of the Gaussian modal field in the three branch structure. Many three-branch structures have been reported to improve the uniformity. The phase wave front accelerator/microprism was introduced to compensate the phase difference between three outputs as mentioned in [15]– [17]. The effective index and the field matching technology reported by Belanger et al. [18]. These two structures both need additional different index material, and thus increased the fabrication difficulty. The MMI structure was also used to obtain three-branch and other 1 × N optical power splitters according to [19] –[21], because of the wavelength dependence characteristic of MMI structure, the WDL of this kind of structure is relatively high. A symmetric three-branch optical power splitter with a coupling gap is demonstrated in [22], [23]. Because of the introducing of coupling gap, the loss increased. Another method introduced a tapered transitional waveguide to reduce the loss as mentioned earlier in [24], [25]. Because of the excited mode is introduced, the radiation loss increased.