Presumably, the light (probably actually the IR, or infrared) leaves the end of
the fiber, and then reflects off a (very nearby, say 10 micron away) flat,
ultra-thin membrane (perpendicular to the fiber) which has been coated to make
it optically reflective. The resulting reflection re-enters the fiber, and
returns to the source. The light source (presumably a laser) is then
optically-mixed with the reflection IR, and this results in an FM-modulated
signal. Jim Bell
From: Blake Hadley <[email protected]>
To: This 1s <[email protected]>
Cc: CypherPunks <[email protected]>
Sent: Thursday, June 16, 2016 12:36 PM
Subject: Re: Turning optical fiber cable into microphone
The way they describe it, they send light down a cable, then watch for the
reflection to come back to them.
The reflection should look the same with every single pulse of light, unless
something affects it, which in this case would be the vibrations of sound.
So it should pick up sound along the entire length of cable, which would return
a lot of ambient noise if you're trying to hear inside someone's house from all
the way back at a utility company.
I don't know how good their audio filtering abilities are, but it seems like
wherever you take measurements can't be too far from what you want to hear.
On Thu, Jun 16, 2016 at 1:56 PM, This 1s <[email protected]> wrote:
Looking for stuff I found this
post:http://blogs.wsj.com/tech-europe/2012/09/04/turning-a-fiber-optic-cable-into-a-microphone/
Is internet cable in house a hot mic?Is it the end of the fiber, the field
around the cable, or both?
Thanks in advance :D
