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Optical Bandpass filter specification

  1. Oct 30, 2016 #1

    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. jcsd
  3. Oct 30, 2016 #2


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    Staff: Mentor

    Can you post a link to a typical datasheet for an optical bandpass filter? :smile:
  4. Oct 30, 2016 #3
    Start with the relation between wavelength and frequency:
    $$\lambda f=c$$ 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
    $$\frac{\left( 3\cdot {{10}^{8}}\ [GHz\cdot nm] \right)}{{{\left( 1550\ [nm] \right)}^{2}}}\left( 0.1\ [nm] \right)\cong 12.5\ [GHz]$$

    Obviously the filter manufacturer will have to specify the filter center frequency for your application.
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