Optical Spectrum Analyzers - Confused on Units

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Discussion Overview

The discussion revolves around the units used in optical spectrum analyzers (OSAs), specifically the confusion between measurements expressed in units of length (e.g., picometers) and frequency (e.g., megahertz). Participants explore the relationship between frequency and wavelength, particularly in the context of resolution and measurement errors.

Discussion Character

  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant expresses confusion regarding the units of resolution quoted by manufacturers, noting the coexistence of length and frequency measurements.
  • Another participant clarifies that the quoted numbers represent differences or errors in the measurements of frequencies and wavelengths, rather than direct measurements themselves.
  • A participant seeks to understand the units of the proportion between the measured frequencies and wavelengths.
  • A later reply indicates that running through numeric examples using the speed of light helped clarify the concepts for one participant.

Areas of Agreement / Disagreement

Participants generally agree on the nature of the measurements as differences or errors, but there remains some uncertainty regarding the specific units of proportion between frequencies and wavelengths.

Contextual Notes

There are unresolved questions regarding the exact relationship and units of proportion between frequency and wavelength measurements, as well as the implications of resolution in practical applications.

cambridgejohn
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Hi!

I am new to these, and off the bat am confused by the units.

Manufacturers quote resolution either in units of length, e.g. 0.04 nm, or HZ. For example,

0.04 pm / 5MHz
0.16 pm / 20 MHz
0.8 pm / 100 MHz.

I am thrown by this since I thought frequency was the inverse of wavelength. I get the length part and can understand when I look at a plot of Power vs. Wavelength.

I know I am overlooking something obvious...please help!

Thanks!
John
 
Science news on Phys.org
The numbers are not frequencies and wavelengths. The are differences between (or errors in the measurement of) in frequencies and wavelengths.

If a frequency f has wavelength \lambda, then
a frequency of f + 5 Mhz has a wavelength of approximately \lambda - 0.04pm, and so on
 
Thanks. The error concept part helps. I can understand when a wavelength is being measured a higher resolution helps out, and that one needs to only buy an OSA which will discern a certain wavelength spectra. And I can understand how the difference part makes sense for the wavelength.

What are the units of the proportion between the frequencies and wavelengths measured?
 
ok. it all makes sense now. just needed to run through some numeric examples using the speed of light to get numbers. thanks again for your help.
 

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