Fig. 1. Schematic diagram of the MMI-based few-mode transmitter.

Fig. 2. Schematic diagram of the mode converter/multiplexer.

Fig. 3. Schematic diagram of the wavelength-mode division multiplexer: (a) general interference N×1 MMI and (b) symmetric interference K×1 MMI.

Fig. 4. (a) Epitaxial structure of the MMI, and (b) the cross section view of the waveguide.

Fig. 5. Field distributions of a 3×1 symmetric interference MMI as a multiplexer (MMI-3) when (a) a fundamental TE0 mode or (b) a first-order TE1 mode is injected into a different input port.

Fig. 6. Wavelength sensitivity of the 3×1 MMI wavelength-mode multiplexer when (a) the fundamental TE0 modes or (b) the first-order TE1 modes are launched from port 1 to port 3.

Fig. 7. Simulated fabrication tolerance for the (a) length and (b) width direction of the wavelength-mode division multiplexer.

Fig. 8. Field distribution when an input TE0 mode transmits through (a–c) MMI-1 and MMI-2 and (d–e) MMI-1, MMI-2, and MMI-3. (a) and (b) are obtained by disconnecting one of the feeding arms to MMI-2.

Fig. 9. Simulated loss vs. wavelength for the whole device (the intrinsic loss of MMIs has been subtracted).