Re: White Light
arunmit168 said:
almost, in all applications an electrical signal is at first converted to optical and then allowed to pass thro the fibre... correct me if i am wrong so inorder to produce an optical white light... it means that an electrical signal with "all frequencies" must bethe source which is being converted to optical? am i interpreting right? is there such a relation existing between the two? or is this a crap? pls explain... if not.. then is this theoretically possible? hope not!
regards,
arunmit168.
No you're are incorrect. The Optical signal is usually a laser at a single wavelength.
The optical wavelength has no relationship to the electrical signal to be transported.
I work with CATV laser transmitters and receivers. We typically convert 80 channels of television onto a single wavelength laser thru fiber. Weither we use 1 or 80 channels the wavelength of the laser remains constant.
There is little difference between the method used to transmit radio or television via airwaves to the same signals sent down fiber optic cable. All are heterodyne transmissions.
Now while white light can travel down a fibre it most likely will be attenuated ( reduced ) due to the fact the fibre is usually defined to a rather narrow band compared to white light which is a mixing of all optical frequencies.
Most fibres are in the 680nm ( red ) to 1500nm range ( infrared )
most common frequencies are 1300nm and 1500nm for CATV.
while white light covers ( to human eye ) from ~400nm ( violet ) to 700nm. ( red )
You can use white light but only part of it will be able to travel down the fiber without significant losses. You can think of the fiber as a filter that will only pass signal within its designated range. thus If you supply a while light (400nm-700nm) to a 680nm fiber eveything below about 600nm is lost. What will happen is you will get a significantly reduced optical power level thru the fiber using white as opposed to the wavelength the fiber is designated for.
Think of it this way the total power in while light is spread evenly across all frequencies from 400 to 700nm summed. If the fiber only passes 680 +-80nm then the amount of power seen thru the fiber would be about 1/3 or less of the applied optical power. IF you only used 1 wavelength at the fibers frequency then you'll see about 98% of the applied power thru the fiber. BIG difference.
hope this helps