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# Single Cavity Filter Tutorial

The Single Cavity Filter (SCF) is used to select a single frequency from a broad spectral range. SCFs are typically used for wavelength locking.

## Center Wavelength (CWL) [nm]:

The center wavelength (CWL) is defined as the mean wavelength @ -3 dB of the SCF e.g.

If the –3 dB bandwidth of the SCF is 1564.825 – 1565.175 nm then the CWL is (1565.175 + 1564.825)/2 ~ 1565.000 nm.

## Band Width (BW) [nm]:

The width of the transmittance curve about the center wavelength at a certain specified transmittance level.