Optical fiber, pass a laser beam thru it
Uhhh, if you value your eyeballs, don't try looking at the laser thru the fiber ever again. If it is a communications laser, it is not visable light.
it is a 5m w laser pointer
single mode laser fiber is designed for one of two wavelengths, both are infra red. A laser pointer has a much shorter wavelength, so the fiber may not transmit it very well. Also, it is very hard to get the laser pointer light into the fiber, so you are probably reflecting most of the light BEFORE it gets into the fiber. The single mode fiber is a lot smaller in diameter than is looks like, most of what you are seing is just the cladding part that does not carry light.
I would recommend using a flexible plastic light pipe. They make these for lighting applications, and carry visable light. Common lengths are 20 feet long, etc.
biff44: it's not for particular wavelength (despite the wavelength with optimal transmission exists). The single mode fiber (SMF) as the name - refers to the single MODE not to single wavelength. Moreover there is no point for going too deep, as for explaining what is happening in SMF the Nobel Prize was awarded to prof. Kao.
Nevertheless the biggest problem is coupling the laser into the optical fiber. The size of the core (the main transmitting part of fiber) is in rage 4-10um. Moreover it's acceptance angle (the angles at which the incident ray can enter the fiber) is few degrees.
In optics where the laser is not a diode - the microscope objective is placed on x,y,theta stage (it can move in two directions and tilt in one or two) sitting in front of fiber holder. Coupling the laser beam into such small stuff is very tricky.
How it's used in telecomunnication - the lasing diode is incorporated at the fiber end, so "all" the light that is produced is coupled in.
Depending on what you want to achieve I will support biff44's idea about lightpipe, or if it needs to be fiber - usethe multimode one - it has bigger core (the BIG ones are above 100um - normally couple of tens of um) and higher acceptance angle.
Best regards,
Micard
Ready made laser diodes with single mode fibre coupler achieve 10 to 40% efficiency, depending on the core diameter,
utilizing actually less than "all" light. They are using micro lenses (e.g. spheres) in most cases. The beam of a laser pointer
has been collimated to several mm aperture to achieve low divergence, so you won't catch more than a few ppm of the
laser power to a single mode fibre without additional optics.
I guess you are right. Found this curve:
http://en.wikipedia.org/wiki/File:Zblan_transmit.jpg
You can shove visible light down a single mode fiber, and even though the loss will be 10X than at 1310 or 1550 nm, you have to have a km of fiber before the difference is even 10 dB.