FTTH Network Testing During Construction

FTTH Network Testing During Construction : When the construction of FTTH network is done, some testing is necessary, which I will discuss in this article. During network construction, some testing takes place at an OSP. When fiber is laid new splices have to be tested and tested using OTDR. Through bidirectional OTDR, we do a lot of accurate measurement, so bidirectional OTDR should be used for testing FTTH networks. Must remember that for accurate measurement of FTTH network must be use Bidirectional OTDR.

For acceptance testing, it is important to test each section of the FTTH construction. There are several testing methods, some of which are explained in this article. Each has specific advantages and disadvantages. Selecting the most appropriate method depends on the constraints encountered: labor cost, budget loss, test time service activation time, maximum allowable measurement uncertainty, etc.

Optical Loss Test of FTTH Network

The first optical loss test is set for FTTH network testing during construction and this test consists of two tests. Consisting of two test sets to measure insertion loss (IL) and optical return loss (ORL). 

Next, ORL sensitivity is determined by calibrating the minimum ORL that the units can measure. It may be possible that the limit comes from the poor part of the test setup, which is most likely to be the connector between the units and the reference test jumper. Actually you have to follow the manufacturer's instructions ORL sensitivity on both units and mentioning source and power meter. 

The measurement of FTTH networks can now be taken on an end-to-end network or any individual installed segment, such as the fiber between the FCB and the drop terminal. Purpose of this test is to identify any transposed fibers and to find out the value of IL and ORL to ensure that the loss has been budgeted.

During the FTTH network measurement a table is prepared for the IL and ORL and the expected ORL values ​​are obtained. In this table Pr = Premises, CO = Central Office Mentioned.

These values take into account only two connections. FTTH networks often include many connection points and, the reflection values are very sensitive to dust and scratches, these values can easily be affected by poor connections.

For example, a single connector might generate an ORL of 40dB, which would exceed the expected value for the entire network. For point-to-multipoint FTTH networks, the ORL contribution of each fiber is increased from 30 to 32 dB due to the bidirectional loss of the splitter.

Advantage of Method Optical Loss Test Sets

There is also some advantage of optical loss test sets in FTTH network, which is mentioned below-

➤Accurate IL and ORL measurement.

➤Bidirectional IL and ORL values.

➤Possibility to test every distribution fiber.

➤The identification of macrobands during the test is performed at 1550 and 1310 nm or another combination of wavelengths, including 1625 nm wavelength.

➤Transposed fiber identification on point to point networks.

➤Fast testing

Disadvantage of Method Optical Loss Test Sets

➤Required two technicians  (however with a point-to-multipoint network, a single OLTS close to the OLT can be used for all subscribers within the same network).

➤Required communication  between technicians (when switching fibers).

➤A point-to-point network is required, a technician has to move from the drop terminal to the drop terminal. 

➤In the event of a cut fiber or macroband, an OTDR is required to detect the fault.

➤Impossible to detect transposed fiber on point-to-multipoint network.

Use of an OTDR for FTTH Network Testing

An OTDR used for this method. Unlike an OLTS, OTDR can identify and locate the position of each component in the network. OTDR will disclose the partition Loss, Connector Loss and Reflection, and Total End to Loss and ORL.

All fibers between the OLT and the first splitter (transport side) can be tested to characterize the loss of each splice and detect macrobands. Both directions test can be conducted.

The calculation of the actual loss (on average between each direction) of each splice will require post-processing of the results. FTTH engineer can measure the loss of the FTTH link like splitter and the loss of the cumulative link, as well as identify whether an unexpected physical event has occurred before or after the splitter. 

During FTTH network construction testing can reduce the number of problems that occur after customer activation by certifying end-to-end link integrity.

Advantages of OTDR Test

➤Measures both IL and ORL values.

➤It is possible to test every distribution fiber.

➤Macrobands are identified at 1550 and 1310nm during testing or another combination of wavelengths involving 1625nm wavelengths.

➤In the case of  fiber cut or macroband, the defect may be located.

➤One technician can perform the job.

➤Fast testing.

FTTH Service activation

Maybe you all find FTTH service activation very easy, although this task should not be underestimated as this is the moment at which the customer experience begins. And the customer also has to maintain trust by giving a good service.

The FTTH network service activation scheme may be different depending on the topology of the fiber network. The trend is for multiple connection points for pre-engineered plug and play components, rather than an all spliced   approach, specifically for deployment in MDUs.

In the context of handling data related to testing and measurement in PON, service activation brings two new dimensions:

➤The results should be linked to customers or ONUs rather than fiber.

➤More than one test space may be required, usually two or three.

FTTH Network Multiple testing locations

Testing engineers assist in verifying optical levels at different locations along the same fiber path to indicate problems and / or faulty components before activating customer service. 

Since FTTH network problems are often caused by dirty or damaged connectors, component inspection greatly reduces the need for troubleshooting, as the power level is verified for each network section.

It is also strongly recommended that each connection point be inspected using a fiber inspection probe before each power measurement.

FTTH Network Testing Points

➤The splitter, or more specifically by performing a power-level certification on the output, enables users to verify whether the splitter branch is functioning properly. This simple estimation makes it possible to confirm whether all network components (including feeder fibers) from the CO splitter output are in good condition. Typically, FDH includes SC / APC or LC / APC connectors, but may also include fusion spices.

➤Operating a power-level certificate at the drop terminal, engineers can mark the distribution fiber and drop terminal ports. Typically, a splice tray is included within the drop terminal that can cause macrobend problems.

➤The fiber connecting the drop terminals and the customer's premises is typically installed during service activation. To ensure reliable services to the customer, Network and Subscriber ONUs must meet their specifications. In FTTH network testing the best way to guarantee this is to perform a pass-through connection to fully characterize all operating wavelengths (upstream and downstream) in the PON. This can only be achieved in the service-activation phase, which uses dual-port PON power meters with power stroke connections; A normal power meter can only authenticate a downstream signal from the CO.

Last Word

In this article, I have tried to explain completely about the testing happening in FTTH network during construction. How did you all like this article "FTTH Network Testing During Construction", comment me in the inbox.