100 feet is probably getting to the limits for plastic fibre. Glass would be preferable - but may be harder to get hold of cheaply. Also, as the core size is smaller, it gets a lot harder to actually launch enough light into the fibre. The problem is not only attenuation but bandwidth, the BW of plastic fibre being quite limited, due to the "stepped index" and large core construstion, while glass fibre is mostly graded index (or for telecom - single mode). I very much doubt that fishing line will get you more than a few metres, proper plastic fibre might do the job, and glass would be fine - but you may need fiddle with the leds to get enough light in. If there is a cable factory handy, you might be able to score scrap lengths of fibre - we used to chuck out anything less than 1km lengths as the cables were always longer than this - but that was mostly single mode anyway. Otherwise, as suggested, a jointing gang may let you have some - but again it is likely to be single mode and very hard to get enough launch power (the core diameter is only about 10 microns). My best bet for fibre type is the 62.5/125 micron glass fibre that was/is?? used for FDDI data transmission - but I have no idea where you might find any going cheap. 50/125 telecom multimode would be OK too but that was getting scarce 10 years ago! IIRC there was also a 100micron core size material but I didn't handle any of it. Also - is using glass - be careful. The fibre is very easily embedded in skin, or eyes etc. and can be very difficult to remove. I still have a small piece in one of my thumbs 10years after last using the stuff. I can only feel it every so often - just enough to remin me it's still there! In order to get light in and out of fibre you need to have a smooth end face. This is mormally acheived with glass by using a special cleaving tool or by polishing the fibre end. You may be able to get a good cleave by scratching the fibre with a hardened steel tool and bending it slightly (wear glasses) - check with a magnifier that the centre of the fibre is a smooth face. If you hold the far end to a light source you should be able to see light coming through the core - once you have cleaved that face also and especially for larger core fibres - single mode can be difficult. Best of luck Richard P Graeme Zimmer cc: Sent by: pic Subject: Cheap Optical Fibre ? microcontrolle r discussion list 24/03/02 00:06 Please respond to pic microcontrolle r discussion list Here's a question.... I can think of umpteen applications, if only I could find a supply of cheap(ish) optical fibre. An example would be a remote Receiving Antenna for VLF (no metalic connection so as to get away from noise). It would feed the sigs down the fibre in simple analog format. The fibre would need to have low enough attenuation to go 100 ft or so and the exciter LED would need to be modulated up to a few hundred Khz. Any suggestions as to manufacturer and or fibre type ? (glass, plastic ?) Is unclad fibre cheaper and/or useable ? Thanks in advance .............. Zim -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics