Fiber question

[ramirez]

Is transmission over fiber analog or digital?

 

[Tomer]

Digital

 

[cmetz]

ramirez, fiber can be used to transmit analog, digital, or both. An example of analog is cable TV distribution. An example of digital is fiber Ethernet flavors. An example of both is BPON or GPON (Verizon FIOS).

 

[Goosemaster]

Originally posted by: cmetz
ramirez, fiber can be used to transmit analog, digital, or both. An example of analog is cable TV distribution. An example of digital is fiber Ethernet flavors. An example of both is BPON or GPON (Verizon FIOS).

what would an analog signal be transmitted as on fiber? Radio waves?


<--would like to learn more since he thought light (laser/LED etc..) were the only methods of traversing these class 'tubes'

 

[futuristicmonkey]

Originally posted by: Goosemaster

Originally posted by: cmetz
ramirez, fiber can be used to transmit analog, digital, or both. An example of analog is cable TV distribution. An example of digital is fiber Ethernet flavors. An example of both is BPON or GPON (Verizon FIOS).

what would an analog signal be transmitted as on fiber? Radio waves?


<--would like to learn more since he thought light (laser/LED etc..) were the only methods of traversing these class 'tubes'

Light in varying intensities, perhaps?

I don't know - I want to find out as well.

 

[cmetz]

Yes, basically you can vary the power of a LED or laser within a certain output region, and it will behave linearly enough, and the detector on the other end can convert it back to an electrical signal linearly enough. I say linearly enough because when you get into the ugly gory physics of fiber, basically nothing ends up really being linear. (really getting deep into the physics of fiber meant math that finally made me cry "uncle")

Most cable TV systems distribute signals from the head end to your neighborhood using analog fiber. Hence the term Hybrid Fiber-Coax (HFC). They basically have to do this in order to meet the noise budget requirements for two-way cable modems.

 

[spidey07]

Originally posted by: cmetz
Yes, basically you can vary the power of a LED or laser within a certain output region, and it will behave linearly enough, and the detector on the other end can convert it back to an electrical signal linearly enough. I say linearly enough because when you get into the ugly gory physics of fiber, basically nothing ends up really being linear. (really getting deep into the physics of fiber meant math that finally made me cry "uncle")

Most cable TV systems distribute signals from the head end to your neighborhood using analog fiber. Hence the term Hybrid Fiber-Coax (HFC). They basically have to do this in order to meet the noise budget requirements for two-way cable modems.

Let's not forget the optical video distrubtion systems for private video networks (security cameras for a large facility for example).

 

[ramirez]

So when digital info is transmitted as pulses then (i.e. on and off), whereas analog info is transmitted in varying intensities.

Does this mean that no modulation is happening when digital info is being transmitted?

 

[kamper]

Originally posted by: ramirez
So when digital info is transmitted as pulses then (i.e. on and off), whereas analog info is transmitted in varying intensities.

Does this mean that no modulation is happening when digital info is being transmitted?

Digital info is transmitted in a very wide variety of ways. Pulses are one (rather simplistic) way to do it (and even then, it's not just "light on" ... "light off").

 

[ForumMaster]

umm, cmetz did youjust make this up? links plz. fiber is digital. attenuation affectes fiber so digital is a must. and you can't vary the strength of the laser inside the fiber. that would ruin the advantage of fiber.

 

[cmetz]

ramirez, there is always a modulation and coding going on to transmit a digital signal. It can be almost as simple as on/off but you need to do something like scrambling to ensure that there's enough bit transitions so the receiver can clock. I'm not an expert on codings used on current fiber, but I'd be surprised if it was dramatically different than what's done over copper, but there are likely to be faster symbol clocks and fewer valid symbols.