# Optical Bandpass filter specification

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1. Oct 30, 2016

### OrangeYogi

Hello,

For optical bandpass filter specification, what do they mean by 0.1nm bandpass filter? What is the equivalent bandpass frequency range of the filter?

Thank you.

2. Oct 30, 2016

### Staff: Mentor

Can you post a link to a typical datasheet for an optical bandpass filter?

3. Oct 30, 2016

### deskswirl

$$\lambda f=c$$ differentiating gives $$\Delta f=-\frac{c}{\lambda _{0}^{2}}\Delta \lambda$$ The negative sign means that an increase in frequency corresponds to a decrease in wavelength. Assume a wavelength for your carrier frequency, a common one for optical communication purposes is 1550 nm. So the equivalent frequency bandwidth is
$$\frac{\left( 3\cdot {{10}^{8}}\ [GHz\cdot nm] \right)}{{{\left( 1550\ [nm] \right)}^{2}}}\left( 0.1\ [nm] \right)\cong 12.5\ [GHz]$$