I Optical spectrum analyzer related

chisuma
Messages
2
Reaction score
0
TL;DR Summary
Can anyone explain why optical spectrum analyzer plots are in negative dB
Can anyone explain why optical spectrum analyzer plots are in negative dB
 
Physics news on Phys.org
chisuma said:
Summary:: Can anyone explain why optical spectrum analyzer plots are in negative dB

Can anyone explain why optical spectrum analyzer plots are in negative dB
Welcome to PhysicsForums.

What optical power would correspond to 0dB? :wink:

Also, which optical spectrum analyzer are you using, and are you using it to measure attenuation in optical fiber?
 
Thanks Berkeman. Appreciate your response. 0 db translates to 1 mW of power. We are using Yokogawa spectrum analyzer. We are measuring power out of the fiber. Please correct me if I am wrong - I think attenuation in the fiber can be calculated by the delta in power between free space power and power out of fiber. Regarding my question as to why there are negative values in OSA spectrum, is it a relative measurement with respect to 1mW power (0 dB).
 
Often (but not always), you'll see dB with respect to 1mW written as units of dBm instead of dB. Its only a valid unit for absolute power. If you're not sure if the dB your spectrum analyzer reports are with respect to 1mW, check if the units say "dBm". If they just say "dB", you may want to test the spectrum analyzer with a signal of known power (like a visual fault indicator, the laser pointer thingy for aligning fibers). Check the signal against a power meter and the spectrum analyzer. (Note: lots of people don't distinguish between dB and dBm so just because your y-axis doesn't say dBm doesn't mean its not with respect to 1mW.)
And yes, the attenuation is typically given as the difference in input and output power on a dB scale (not a linear scale!) divided by the length of the fiber in km.
 
I am not sure if this belongs in the biology section, but it appears more of a quantum physics question. Mike Wiest, Associate Professor of Neuroscience at Wellesley College in the US. In 2024 he published the results of an experiment on anaesthesia which purported to point to a role of quantum processes in consciousness; here is a popular exposition: https://neurosciencenews.com/quantum-process-consciousness-27624/ As my expertise in neuroscience doesn't reach up to an ant's ear...
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. Towards the end of the first lecture for the Qiskit Global Summer School 2025, Foundations of Quantum Mechanics, Olivia Lanes (Global Lead, Content and Education IBM) stated... Source: https://www.physicsforums.com/insights/quantum-entanglement-is-a-kinematic-fact-not-a-dynamical-effect/ by @RUTA
This is still a great mystery, Einstein called it ""spooky action at a distance" But science and mathematics are full of concepts which at first cause great bafflement but in due course are just accepted. In the case of Quantum Mechanics this gave rise to the saying "Shut up and calculate". In other words, don't try to "understand it" just accept that the mathematics works. The square root of minus one is another example - it does not exist and yet electrical engineers use it to do...
Back
Top