# Mode
Editor: Create New Project › MODE · Python: td.ModeSimulation
A Mode project computes the optical modes of a waveguide cross-section. A mode is a field pattern that travels along the waveguide without changing shape. For each mode, you get its field profile, its effective index and its group index, at each wavelength.
To see how light travels through a whole device, use an FDTD project. For long waveguide devices, an EME project can be faster.
To start, follow Create Your First Project and choose the MODE tab. For a complete example, follow Find the Modes of a Waveguide. Then set up:
- Structures in the Model tab. A new Mode project offers Waveguide Templates.
- Mode Specifications in the Setup tab: the number of modes, the wavelengths and more.
- Mode Plane in the Setup tab: the cross-section to solve.
- Configuration in the Setup tab: the domain, the grid, the boundaries and the symmetry.
- Script Objects, if you need them.
Then click Check Simulation, run the simulation, and open the Results tab. If something goes wrong, see Mode Troubleshooting.