Inspecting Transceiver Tx and Rx ports

Applies to

FIP-400B series, FIP-500


Can I use the FIP-400B and/or FIP-500 to inspect the ports of a transceiver?


Yes indeed we can and should use EXFO fiber inspection tools to inspect transceiver ports.

However,  understanding how transceivers couple light TO (Tx) and FROM (Rx) the fibers will go a long way in helping you understand some of the challenges related to inspecting the Tx and Rx ports of  a Transceiver.

This article is presented in 2 sections;

  1.  Practical information regarding transceiver inspection
  2.  Understanding how transceivers couple light to and from the fiber


Section A - Practical information regarding transceiver inspection

1.  EXFO Software

In version 3.25 of ConnectorMax 2, there is a new inspection mode/configuration that includes Single fiber transceiver and Multifiber transceiver.

2. IEC Standards 

  • In the IEC standard no acceptance criteria are defined for the Rx side. (keep reading to understand why).
  • On the Tx side, sometimes referred to as the “Fiber Receptacle”, acceptance criteria are defined.

3. Cleaning

  • Most cleaning material vendors do not have specific tools for cleaning the Rx side of the transceiver.
  • The reason being that many transceiver manufacturers are NOT recommending to clean the Rx port.
  • The lens inside the Rx port is not very sensitive to soiling and scratches

4. Inspection probe measurement principle

In a fiber inspection probe, a LED will send light into the port and the reflections are captured by a camera in the probe. If the element is transparent (lens for example), only a small % of the light will be reflected back and therefore the FIP may not always see the lens.
5. General Procedure for inspecting the Rx port of a transceiver
  1.  Select the appropriate tip for the Port type, and attach to the FIP.
  2.  Insert the tip into the Rx port.
  3.  Adjust the focus all the way to the shortest distance, Right or Clockwise.
  4.  Begin adjusting the focus (Left or Counter-Clockwise) so that the focus plane moves towards the interface elements.
  5.  Stop when you see an image come into focus.
  6.   Depending on the type of lens interface being inspected, different images will come into focus.
  7.  Continue until you see the outer most lens. You will be able to see the ring around the lens in some cases and that will give an indication that the focal point is at/near where the lens is located.
  8.  You can capture this image, and if it is included in your company's procedures, it may be cleaned where severe soiling is observed.
  9. You may want to continue moving the focal point towards the "bottom" of the ROSA, seeing other images, however only the outermost lens surface may be potentially cleaned. 


 Section B - Understanding how transceivers couple light to and from the fiber

in this section, to help explain we are using the example of an SFP transceiver with LC optical ports as shown below.

Transmit Side (Tx)

On most transceivers, the transmit side ( TX or TOSA) contains a physical contact fiber stub, and the inspection is very similar to inspecting a standard bulkhead-connection.

  • On the TX side, you will be able to take a clear image of the fiber stub end-face, and depending on FIP model and options, make a full analysis for defects in accordance with a standard or your own criteria.
  • Sometimes there may be a coating on the fiber stub end-face or other sources of reflection. As such, it is recommended to use the appropriate transceiver test configuration that take this into consideration. 
  • The fiber stub should be clean and without defects for optimum performance.

                           Clean Fiber stub

Receive side (RX)

On the receive side (RX or ROSA), light is coupled from the fiber end and is focused to a focal point on the Detector surface. One or 2 lenses are used to ensure that the Detector captures as much of the signal as possible. 

  • Example ROSA-1 has 2 lenses, A physical contact Special lens and a ball lens that work together to focus the light to the back end of the assembly onto the receiver detector
  • Example ROSA-2 has a ferrule stop followed by a single ball lens focusing the light onto the detector.
  • Because neither lens is at the focal point, the RX is less sensitive to soiling. For this reason, some transceiver manufacturers do not recommend cleaning, so as to not damage the internal lenses.
  • The lenses do not reflect much light and therefore it is difficult to autofocus with the fiber inspection probes.
  • A manual focus will allow you to see the different surfaces, either the detector surface, the ball lens, and inner and outer surfaces of the special lens (if present)


In summary:

  • inspecting the Tx side is normally similar to inspecting other connectors,
  • Inspecting the Rx side may be more tricky for the reasons explained above.

Please contact our technical support team if you have further questions.