## 1 Introduction  
In recent years, high bandwidth demands have been due to the worldwide deployment of the Internet-of-Things (IOT), big data analysis, on-line gaming and shopping, video streaming, and many different internet-based services [1; 2; 3; 4; 5; 6; 7]. For the data center networks, the electronic interconnect data rates are limited by high power consumption. Hence, silicon photonics (SiPh) are considered a promising technology for increasing interconnect speed and capacity while decreasing the power consumption [8; 9; 10]. SiPh devices are fabricated using mature complementary metal oxide semiconductor (CMOS) fabrication technologies; hence, high yield and efficient SiPh devices can be implemented [11; 12; 13; 14]. To enhance the SiPh interconnect transmission capacity, different technologies have already been proposed, such as wavelength division multiplexing (WDM) [15; 16], polarization division multiplexing (PolDM) [17; 18] and spatial division multiplexing (SDM) [19; 20], as well as advanced digital multiplexing schemes, e.g., orthogonal frequency-divisionmultiplexing (OFDM) [21], non-orthogonal multiple access (NOMA) [22], etc. Mode division multiplexing (MDM) [19] is a popular way to achieve SDM, which allows signals to be propagated in different orthogonal modes in a single waveguide core. MDM systems using few-mode optical fiber (FMF) were also reported [23; 24]. Different fiber-based or free-space optics-based MDM multiplexer/demultiplexers (Mux/Demux) were demonstrated, including those utilizing directional mode selective couplers [25], long period fiber grating (LPFG) [26], free-space optics [27], and photonic lanterns (PLs) [28].  
Alongside the fiber-based and free-space optics-based MDM Mux/Demux, SiPh based MDM Mux/Demux is easier to realize as different modes transmitting in a waveguide core can be easily preserved and converted in the planar waveguide structures. Using an asymmetrical directional coupler (ADC) is a sample way to achieve wideband, higher conversion efficiency and low crosstalk MDM Mux/Demux on a silicon-on-insulator (SOI) platform [19; 20]. Wideband MDM components, simultaneously supporting WDM and OFDM, can significantly increase the transmission capacity for optical interconnects. A power divider is one of the basic building blocks for SiPh on-chip networks; and dual-mode and triple-mode on-chip optical power dividers were successfully demonstrated recently [29; 30; 31]. These MDM building blocks can allow the realization of future multi-mode photonic integrated circuits (PICs) [32]. However, traditional on-chip optical components usually support single-mode operation.  
In this work, we propose, fabricate and demonstrate a wideband and channel switchable MDM optical power divider on an SOI platform, supporting single, dual and triple modes. The switchable MDM power divider consists of two parts. The first part is a cascaded Mach-Zehnder interferometer (MZI) for switching the data from their original transverse-electric (TE) modes, TE\({}_{0}\), TE\({}_{1}\) and TE\({}_{2}\), to different modes among themselves. After the target modes are identified, mode up-conversion and Y-branch are utilized in the second part for the MDM power division. Here, 48 WDM wavelength channels carrying OFDM data are successfully switched and power divided. An aggregated capacity of 7.682 Tbit/s is achieved, satisfying the pre-hard-decision forward-error-correction (pre-HD-FEC) threshold (bit-error-rate, BER = 3.8 \(\times\) 10\({}^{-3}\)). Although up to 3 MDM modes are presented in this proof-of-concept demonstration here, the proposed scheme can be scaled to higher order modes operation.