High-order Mode Pass Filter for Space Division Multiplexing by Using Coupling Principle

Abstract

As the development trend of communication technology, the demand of data amount and transmission data rate are increasing rapidly. The global data traffic will up to more than 200 Exabyte/month by expectation, which is enough to store 9 million years HD video. In global data transmission, more than 90% of the data is dominant by transmitted through submarine cable, which is the optical fiber. However, the data rate of a single fiber is limited at 100 Tbit/s by the physical properties of itself, due to the non-linearity properties. A solution is needed to extent the data rate for future communication, and there are several inventions, such as dense wavelength division multiplexing (DWDM), time division multiplexing (TDM), erbium-doped optical fiber amplifier (EDFA), etc. All these advanced technology already pushed the data rate up, but still cannot overcome the limitation. In the remaining area, the space division multiplexing (SDM) is one of the most potential approach that can be improved the optic communication system. To realize a SDM system, apart from multimode (MM) fiber used, we also need to develop a new set of MM devices at the receiver and the transmitter. Such devices includes mode converter, multiplexing (Mux) and Demultiplexer (Demux), also with the mode filter. Among all these devices, mode filter is the least design available in the current system. In this project, we proposed a broadband nth order mode pass filter design. In the design, we use the planer lightwave circuit approach, because the design is simpler and mass productive over other approach. Our design has a unique advantage that it is scalable through all SDM system. The design can be applied on any high order mode pass filtering without cascading, for implementing the directional coupler as the mode converter, and using the coupling principle also with the properties of single mode (SM) fiber to achieve the filtering purpose. The fabrication is done under standard microfabrication process, and polymer is used for the device materials, since polymer waveguide has the ability to provide optical input to flexible devices. A 2nd order mode (TE2) pass filter is fabricated to demonstrate the design. The wavelength from 1.530 to 1.566μm (C-band) is used to experiment the performance of the device. The simulated result of 2nd order transmission, 24dB and 29dB were the average extinction ratio respectively, and 0.24dB was the transmission loss.