vin_sys 0 Posted February 28, 2009 We had installed 10 PTZ cameras in line over 10 Kms dropping 1 pair of fiber at each camera location. Now the problem is Video from all the cameras are being displayed clearly, but the data (PTZ command) is working for only 1-2 cameras . earlier it worked well for 7 cameras. We had used ONV make Fiber convertors. My doubt is - if video is crystal clear from all sources , then why the data is not operating. I had also checked for all type of RS 485 leakage, terminations etc. Also tried installing single camera over 7th KM (removing all other cameras ) but in vain. PLEASE HELP SOMEONE. Share this post Link to post Share on other sites
vadsys 0 Posted March 2, 2009 hi vin_sys, there are lots of possiabilities on this issue may happen. 1st, go check the optical power output,link loss.perhaps the optical attenuation was changed 2ed, do you mean you use the cascade solution with two fibers go through all the 10 cameras in line, just like series-wound?if it is true, maybe it is the F.O. system not so stable, check this with the rep. of ONV. any question, just feel free to send me PM or contact me directly: vad.joseph @ gmail . com btw, we have full range of F.O. solutions, next time may try ours attached the solution scheme for you reference cascade fiber solution.rar Share this post Link to post Share on other sites
vadsys 0 Posted March 3, 2009 We had installed 10 PTZ cameras in line over 10 Kms dropping 1 pair of fiber at each camera location. Now the problem is Video from all the cameras are being displayed clearly, but the data (PTZ command) is working for only 1-2 cameras . earlier it worked well for 7 cameras.We had used ONV make Fiber convertors. My doubt is - if video is crystal clear from all sources , then why the data is not operating. I had also checked for all type of RS 485 leakage, terminations etc. Also tried installing single camera over 7th KM (removing all other cameras ) but in vain. PLEASE HELP SOMEONE. mostly the problem is about the attenuation of the fiber,as i mentioned in my pre-post, check the optical output power first. you know, for video transmission from camera to monitor, the wavelength is 1310nm, but for the reverse data to the camera, the wavelength is 1550nm.so if the link loss is beyond the budget loss, video still can be displayed,but data can not be arrived at cameras If the fiber has been laid for years,or over soldered, they may casued a big link loss. Share this post Link to post Share on other sites
aoshifiber 0 Posted March 3, 2009 hi, friend, i just asked our technical supervisor, he told me if your system is parallel connection to the DVR, maybe the damage of the DVR's data module can cause this problem maybe it's not because of the fiber transceivers Share this post Link to post Share on other sites
bolinboy 0 Posted April 13, 2009 The most common cause of failure of data links over fibre is due to delay timing, biasing errors or on RS485 links, termination errors. The delay timing is used to ensure the data transmit is complete before the RS485 driver changes state for the response. When equipment is installed at remote locations, the local earthing (grounding) is often very different. This leads to a mismatch in reference levels of the copper signal segments between the two ends of the fibre link. Biasing on a fibre tranceiver allows the relative reference levels to be adjusted to a better match. Most fibre optic tranceivers for CCTV use have dipswitch or rotary switches to adjust these settings. Check with your manufacturer for the adjustments available on your tranceivers and then try them out until you find the best match. If these switches are not available, you will need to use resistors/diodes to create the necessary biasing/termination values. Share this post Link to post Share on other sites
shaggybaxter 0 Posted April 14, 2009 Hi Vin_sys, One issue you need to be aware of is macrobending in the fibre. Too tight a bend in the fibre cable at any point in the cable is called macrobending (a radius of 30mm in a joint on SM fibre will macrobend). An unpleasant side effect is macrobending will pass 1310nm with minimal loss (atypical 1db), but heavily attenuate the 1550nm wavelength (atypical 10db). this means your video will work fine, but your RS data won't. If vadsys is correct and these converters use a 1550nm wavelength, get an OTDR trace of the fibre, could well be macrobending. What's the bet you have a massive attenuation spike somewhere in the cable? javascript:emoticon(':wink:') Share this post Link to post Share on other sites
