Compact triplexer based on silicon nanowire waveguides

Downstream data and downstream video signals at 1490- and 1550-nm wavelengths are downloaded to the users by the 2×2 MMI, while upstream data carried by 1310-nm wavelength is uploaded to the central office by the reflection of Bragg grating.

The researchers, led by Prof. Fuwan Gan, from Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, designed a compact triplexer based on silicon nanowire waveguides. Because of the high index contrast between silicon and silicon dioxide, the size of the structure is greatly reduced with a footprint of 2.5×911（μm）. Besides，the design satisfied the bandwidth requirements of the industrial standards ITU-T G.983. It is reported in Chinese Optics Letters Volume 11, No. 4, 2013 (/col/abstract.cfm?uri=col-11-4-041301).

Fiber-to-the-home (FTTH) system has been developed to meet the ever-increasing demand for bandwidth. Triplexer, as one of the key components in FTTH system, is widely used to provide a triple play service, i.e., the wavelengths of 1310, 1490， and 1550 nm carry upstream data, downstream data， and downstream video signals, respectively. The cheap and compact triplexer has an enormous market demand. In response to this demand, the researchers designed a compact triplexer based on silicon nanowire waveguides, and the device can be readily fabricated using a commercial CMOS process.

The industrial standards ITU-T G.983 has a special bandwidth requirements, where 3-dB bandwidths of 100, 20, and 10 nm for wavelengths λ =1310, 1490, and 1550 nm are required respectively. Traditional structures were difficult to meet the bandwidth requirements. In order to meet the special bandwidth requirements, the researchers embed the Bragg-grating into the 2×2 multimode interference (MMI) coupler to de/multiplex the three wavelengths, and the asymmetrical ports were introduced in the MMI structure to satisfy the bandwidth requirements. 3-dB bandwidths of 100, 22, and 15 nm were obtained for the wavelengths of 1310, 1490, and 1550 nm, respectively.

"The fabrication of the triplexer is planned and we are now coordinating with the fab," Prof. Fuwan Gan adds, "the experimental results will be reported in future work."

硅基集成单纤三向复用器

说明：2×2多模干涉器将1490 nm和1550 nm的信号下传给终端用户使用，同时终端用户通过布拉格光栅的反射将1310 nm的信号上载给数据中心。

中国科学院上海微系统与信息技术研究所甘甫烷研究员课题组基于硅纳米线光波导，利用硅与衬底二氧化硅之间的高折射率差，设计了一种集成单纤三向复用器，该单纤三向复用器的尺寸仅为2.5×911(µm)，同时还可满足ITU-T G.983标准对1310 nm, 1490 nm和1550 nm这三个工作波长的带宽要求。该研究成果将发表在Chinese Optics Letters 2013年第4期上(/col/abstract.cfm?uri=col-11-4-041301)。

随着互联网的高速发展，人们对带宽的要求越来越高。光纤到户(FTTH)技术可向用户提供极丰富的带宽，是一种理想的接入模式。单纤三向复用器是其中最为关键的波分复用器件之一。其主要功能是为用户提供三向数据传输的综合数字业务，数据中心通过1490 nm和1550 nm这两个波长分别将下行的数据信号和视频信号经单纤三向复用器提供给用户终端，而用户可以通过1310nm的波长将本地数据上载到数据中心。因此低成本、小型化、高集成度的单纤三向复用器将有巨大的应用前景。针对这一需求，研究人员利用硅纳米线光波导平台，设计了一种集成单纤三向复用器，其制作工艺与CMOS工艺完全兼容。

国际电信标准化组织的ITU-T G.983标准对单纤三向复用器的1310 nm, 1490 nm和1550 nm这三个工作波长的3-dB带宽有着十分特殊的要求，即要求1310 nm, 1490 nm和1550 nm这三个波长的3-dB带宽分别达到100 nm, 20 nm和10 nm。传统的设计几乎很难完成这样的带宽要求。为了满足差异化如此大的带宽要求，研究人员采用在2×2多模干涉器上浅刻蚀布拉格光栅的方法实现了三波长的波分复用，同时利用非对称的MMI端口成功实现了差异化的带宽要求。

目前，这款单纤三向复用器正在进行流片加工，相关的实验结果将在后续的工作中进行报道。