eriks@yetti.UUCP (11/24/87)
American Photonics Inc. manufactures something called an RL-5000. They call it a 'Fiber Optic Ethernet Expander'. What it is supposed to do is to extend a transceiver cable over a fiber optic link (up to over 3km). It appears to be a convenient way of extending the distance serviced by an ethernet without eating into the repeater budget. I've got a pair of these boxes on a trial basis to check them out but have been having some difficulty in getting them to work. It appears that the boxes work SOMETIMES (!!) (i.e. they pass DECnet HELLO's but nothing else... or they let me initiate a telnet connection but then stop passing packets). My test setup currently uses about 25 ft. of fiber optic cable (62.5/125 micron). The planned installation will use about 1400 ft. of fiber. API thinks that perhaps because the fiber run is so short it is possible that the optical inputs are being over-driven and hence data is not passing through cleanly. I think that I'll just ask them to send over another couple of units to see if they behave the same way. I'm just a little bit reluctant to go ahead and install the full 1400 ft. of fiber, only to find out that my terminating equipment won't work. Does anyone out there have reasonable theories or experiences w.r.t. driving optical stuff at close to 0 dB? (it might be as little as -1dB) Does anyone out there have any experience with this product? (good? bad?) Thanks for any help, Eriks
phil@amdcad.AMD.COM (Phil Ngai) (12/01/87)
In article <209@yetti.UUCP> eriks@yetti.UUCP (Eriks Rugelis) writes: of problems using an >American Photonics Inc. RL-5000. >They call it a 'Fiber Optic Ethernet Expander'. I'm not in networking but I used to be. The following remarks are personal opinions and are not to be associated with my company. We tried using the RL-5000 once. The project was started before I joined the group. I have misgivings about using these transceiver cable extenders, which is what they really are. First of all, the heartbeat gets delayed. Second, your data echo gets delayed. Though many pieces of equipment may work, who's to say someone won't design a piece of equipment which knows that transceiver cables are never longer than 50 meters? I do believe the RL-5000 can work in many situations. It didn't work in ours but that was later found to be probably our fault. However, API was involved and failed to diagnose the problem even though it was possible for them to do so and save the sale. So if you don't mind that a vendor's knowledge of Ethernet may be limited, then you may want to use the RL-5000. In our case, it turned out to be a mismatch between Ethernet V1 and Ethernet V2 in terms of AC/DC drive. By that time, however, I had already put in DEC DEREPs and API had been designed out. So check for compatibility between your RL-5000, your transceiver, and your DTE. >API thinks that perhaps because the fiber run is so short >it is possible that the optical inputs are being over-driven and hence >data is not passing through cleanly. I think that I'll just ask them >to send over another couple of units to see if they behave the same >way. I'm just a little bit reluctant to go ahead and install the full >1400 ft. of fiber, only to find out that my terminating equipment >won't work. While our vendor was trying to make the RL-5000 work, they brought in something you should know about. It was a black box with 1000 feet of fiber in it, to simulate real installations. I forget the product name or number but it was also made by API. It was claimed to be extremely expensive because of the cost of all the fiber in it. So they may not be willing to loan it to you unless you press them for it. Good luck. I'd be interested in hearing how it turns out. -- I speak for myself, not the company. Phil Ngai, {ucbvax,decwrl,allegra}!amdcad!phil or amdcad!phil@decwrl.dec.com
eshop@saturn.ucsc.edu (Jim Warner) (12/01/87)
In article <19386@amdcad.AMD.COM> phil@amdcad.UUCP (Phil Ngai) writes: >In article <209@yetti.UUCP> eriks@yetti.UUCP (Eriks Rugelis) writes: >>They call it a 'Fiber Optic Ethernet Expander'. > >.... First of all, the >heartbeat gets delayed. Second, your data echo gets delayed. Though >many pieces of equipment may work, who's to say someone won't design a >piece of equipment which knows that transceiver cables are never >longer than 50 meters? The problem of delayed data is occurs with broadband transceivers (Chipcom) and other fiber optic transceivers (Codenol) as well. In a broadband system, the signals must travel all the way to the head end before they are returned to the receiver section. There is definitely lots of equipment that will not tolerate this delay. These transceivers provide local (faked) echo. The Codenol rep told me there is a jumper internal to the transceiver to disable local echo, but there is never any reason to change it. I would be real suprised if the "Ethernet Expander" didn't do the same, but it is definitely a good question to ask. jim warner eshop@saturn.ucsc.edu