One of many challenges with bi-directional (bi-dir) OTDR testing is the logistics and the quantity of inexpensive, accessible, or required check tools.
A single-unit method is normally thought-about to try to save on price—one piece of check tools versus two and one tech versus two—nevertheless it has its drawbacks. For one, it doesn’t confirm continuity. This can be a small however essential factor, as verifying continuity ensures that you’re testing the identical fiber in each instructions and that the hyperlink is terminating on the right patch panel (or different) location. However that’s not the most important subject. With a single-unit method, a tech (and instrument) should check fibers from one finish of a hyperlink, then relocate to the opposite finish of a hyperlink and check from the opposite route. What’s lacking right here is the implementation and connection of a obtain fiber. Mainly, nevertheless you do it, you’re going to wish a second tech.
A fiber hyperlink that has been bi-dir OTDR examined however with out the usage of a obtain fiber means you possibly can carry out bi-dir evaluation (loss averaging) for the hyperlink parts (i.e., splices) however solely uni-directional (uni-dir) for the tip connectors. This implies you haven’t absolutely bi-directionally licensed the hyperlink and as such it’s a non-standard certification.
So the best way to deal with this with only one OTDR?
You would go for loopback method, which permits the tech with the OTDR to handle connection of a obtain cable, nevertheless it means an additional tech is required on the far finish to handle connection of a loopback machine. However the greater subject with loopback testing is you possibly can solely check half the gap that your OTDR is able to as you’re testing two fibers on the similar time.
You should additionally make sure that the strategy used for bi-dir OTDR testing consists of the usage of each launch and obtain fibers as a way to measure and characterise the connector ends of a hyperlink. In that method you’re absolutely compliant and testing to the business requirements.
Why would any darkish fiber buyer, service supplier, or community proprietor wish to take possession of fiber that hasn’t been licensed accurately/absolutely to a recognized normal? The reply is that they wouldn’t (or a minimum of they shouldn’t).
Some single unit approaches are simply plain unsuitable, and by that I imply they don’t adhere absolutely to the requirements for bi-dir OTDR check. These are generally known as asynchronous, and may omit obtain fibers, which may depart you unable to carry out the averaging of measurements for these finish connectors and depart you with an incomplete set of bi-dir outcomes and due to this fact incomplete or non-standard certification.
The VIAVI method with two devices takes care of all of this precisely how the requirements specify and does it with no further handbook effort or interruption to check circulate and workflow.
In a future weblog on this collection I’ll take a look at bi-directional check processes utilizing two devices and the best way to obtain full bi-directional fiber certification (IL, ORL and OTDR) in probably the most environment friendly method.
To be taught extra, check out our Bi-directional OTDR Testing web page.
Dou
glas Clague is at present options advertising and marketing supervisor for fiber optic area options at VIAVI. Doug has over 20 years of expertise in check and measurement with a major deal with fiber optics and cable applied sciences, supporting the telecommunications business. Previous to VIAVI, Doug held positions as manufacturing engineer, options engineer and enterprise improvement supervisor. Doug has participated on quite a few business panels round fiber and cable expertise developments. He attended Brunel College in London and graduated with an honors diploma in electrical and digital engineering.
