bidirectional fibre tranceivers - Page 1
Forum section: electronics / projects

author: Tangent_Tracker
author_rank: Regular Contributor
timestamp: October 21, 2021, 10:47:24 am
content: Hi folks, so we use small PCB mount ST fibre transmitters/recievers (Broadcom/Avago) at work for fibre connections of about 200m. We are a bit low on fibres at the moment and so I started looking for bidirectional devices. You can get these as complete units that will plug directly into network cards/switches etc, but what I would like is a unit that I can mount to a PCB (or with a standard connector) that simply has a UART port or even direct laser access as in the above modules.Short of hacking one of these commercial offerings, does anyone know of any units available with a much-simplified interface, as I cannot find anything!

author: PartialDischarge
author_rank: Super Contributor
timestamp: October 21, 2021, 10:58:54 am
content: I guess you mean bidirectional modules but not over the same fiber cable.Is it 1mm plastic fiber you are using?What speed ? Does it need to be full duplex or can it be half duplex?

author: Tangent_Tracker
author_rank: Regular Contributor
timestamp: October 21, 2021, 11:12:47 am
content: No, same fibre. The modules I have seen use two different wavelength lasers and obviously have internal beam splitters etc...Just surprised the modules are not available to interface to directly for OEM use!https://www.google.com/search?q=Bidirectional+SFP+Transceiver&rlz=1C1CHBD_en-GBGB795GB795&oq=Bidirectional+SFP+Transceiver&aqs=chrome..69i57j69i61l3&sourceid=chrome&ie=UTF-8

author: mikerj
author_rank: Super Contributor
timestamp: October 21, 2021, 01:07:11 pm
content: The keyword you are looking for is "BOSA" Bi-directional Optical Sub-Assembly. I very much doubt you are going to find one with a UART output though.http://www.eoptolink.com/product-solutions/osa/bosa

author: jeremy
author_rank: Super Contributor
timestamp: October 21, 2021, 01:10:06 pm
content: Yes, you can buy these at the local computer supply store now, even TP-Link make them.I don’t know of any that are non-SFP unfortunately, but I would like to know if anyone finds them. Usually SFP modules I have played with (dual fibre) can be used way below their rated data rate though, so it may work for you; for example, a 4Gbps module from Finisar worked fine with a 10MHz square wave.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 21, 2021, 01:11:33 pm
content: Have you considered multiplexing multiple links into a single higher bandwidth link? Ethernet switches with VLAN would be one way, but if the application is really latency sensitive, a pair of small FPGA boards could also work.

author: Renate
author_rank: Super Contributor
timestamp: October 21, 2021, 08:17:53 pm
content: Hey! I was wondering the same thing, but not full duplex, only half duplex.I thought a drop-in RS-485 would be cool. I was originally thinking that 1mm plastic fiber for short distances.Still, even a one way transmitter or receiver costs $10!

author: daddario
author_rank: Regular Contributor
timestamp: October 21, 2021, 08:33:28 pm
content: In networking gear how it's done is using different wavelengths - be it bidirectional, or BIDI as it's called in the trade, using two wavelengths from the 1310~1550nm range (on one side it'll have, for example, a 1310nm transmitter, a 1490nm receiver and vice-versa on the other side) optically coupled together. Or CWDM/WDWM technology that uses tens of different wavelengths on a single fibre and (de)multiplexed together in an external optics units - in all those cases the active parts themselves have their unique WL. If your product is low-volume the cheapest option would be to buy CWDM SFP modules and rip the optics and transducers out.Mind you that technology is intended for single-mode fibre (9/125um), but for very short distances any ol' plastic straw will do.