Principle of OTDR

OTDR (Optical Time Domain Reflectmeter) is a measurement instrument for identifying optic fiber transmission features. The instrument is mainly used to measure attenuation of a whole optic fiber chain and provide attenuation details relating to length, namely detect, locate and measure any event in optic fiber chain (events refer to faults caused by welding, connectors, and bending whose transmission change can be measured). Its non-destructive, one-end connection, and rapid measurement has made the OTDR an indispensable tool for manufacture, construction, and maintenance of optic fiber.

The faults and heterogeneity of optic fiber itself cause Rayleigh scattering of light pulse transmitted in optic fiber. Part of light pulse is scattered in the reverse direction, and this is called Rayleigh backward scattering, which actually provides attenuation details relating to length.

Information relating to distance is obtained through time information (that’s the reason why there is “time Domain” in the name of OTDR). Fresnel reflection occurs at the boundary between two media of different IOR (for example, connections of faults, connectors, or optic fiber end). This reflection is used to locate the discontinuous points on optic fiber. The magnitude of reflection depends on the difference between IOR and the smoothness of boundary.

OTDR sends out a light pulse into connected optic fiber, and receive reflections of events and backward scattering power of pulse in time. Locus will be displayed on LCD. The y-axis is dB value of backward scattering power, and the x-axis is the distance.

Choose OTDR based on your application

Cover dead zones and enable loss measurement on first and last fi ber connectors. Available as modular (FTB-LTC),
portable (SPSB) and stand-alone (PSB) in lengths of 150, 300, 500, 1000 and 2200 m.

Remove uncertainty in testing high-speed multimode network. An external EF-compliant device like the SPSBEF-C30 ensures a fast and easy way to fi x faulty networks (as per TIA -526-14-B and IEC 61280-4-1 Ed. 2.0).

Offered as stand-alone or paired with the test platform, power meters assess fi ber link power levels and establish
basic loss measurements. 7 to 10 calibrated wavelengths and high-power options are available.

Integrated or stand-alone, a VFL easily identifi es breaks, bends, faulty connectors and splices, or other causes of signal loss. Basic yet essential, it should be part of every fi eld technician’s toolbox.

Connect your platform anywhere, anytime. Push data to the cloud, to a device or acquire a platform’s location via GPS.

All your tools within hand’s reach and an extra layer of protection for your OTDR to face outside plant conditions. Available for the MaxTester 700B series and FTB-1 platform.

All-in one OTDR Measure OTDR, return, and insertion loss on a single port to characterize optical links(二)

In a second step, the laser optical power is adjusted so that the measured power is PTX = −6.5 dBm at the end of the patchcord. After performing any of these references, the patch cords must remain connected to the measurement units or an IL variation will occur upon reconnection. In addition to the LB reference procedure, ORL link measurements require knowledge of the zero-offset ORL power, or the measured power P0, due to the return loss of the unit. Figure 1c shows how to perform the zero-offset ORL reference. Connecting the patch cord J1 between the unit and a non-reflective termination ensures a very low return loss. During the zero-offset ORL reference, the laser emits as the power meter on the same port measures the reflected optical power, P0, which is linked to the directivity of the 3-dB coupler inside the measurement unit and to the return loss of the mated connectors at the unit output.

After completing the reference procedures, perform the link measurement step shown in Figure 2. Connect each of the units and their associated patch cord to either side of the link under test. IL and/or ORL measurements can then be performed on one or both units during the same test. The measured data is then displayed on both units. IL should be 40 dB or less, so that the two measurement units can communicate correctly with each other.

All-in one OTDR Measure OTDR, return, and insertion loss on a single port to characterize optical links(一)

The ever increasing number of subscribers together with increasing demand for more and more bandwidth means providers must install fiber optic cables more quickly. Verifying compliance with system manufacturer specifications is required during the installation and acceptance testing phase [1]. These tests should be easy to perform so that the field operators can run them in less time. The new JDSU tool set offers an integrated test function that reduces testing time and deployment costs. To the best of our knowledge, no other commercially available product combines an OTDR and a loss test set that automatically performs these tests through a single optical connection. In this paper, we present a tool set enabling fast insertion loss (IL) and optical return loss (ORL) measurements using optical continuous wave techniques and characterizing its performance using theoretical analysis and experimental validation. Currently, users can choose among these tested wavelengths 1310, 1550, and 1625 nm.

The tool set comprises a set of two measurement units referred to as Units A and B, each plugged into a base platform. Each unit includes multiple lasers and an optical power meter combined in a single fiber output using a 3-dB coupler as in any OTDR. These devices may operate with continuous wave (CW) light in addition to pulsed light used for OTDR operation. Each base platform may also integrate an additional optical power meter that is required for ORL measurements. For correct operation, users should perform a reference procedure before the link measurement, as Figure 1 shows, which may be completed using either the side-by-side (SbyS) or loopback (LB) method. Additionally, a zero-offset ORL reference is needed for ORL measurements.

The SbyS reference mode can be used to perform IL measurements. The two units are connected to each other, as shown in Figure 1a, using two patch cords, J1 and J2. The reference step enables the power meters for both units to measure the optical power PTx emitted by the laser of the other unit minored by the IL of the two patch cords.

However, it may not always be possible to perform this procedure because of the distance between each end of the link being tested; therefore, technicians can use the LB reference mode, as described in Figure 1b, where each of the units is connected to the power meter of its base platform. During the LB reference, the insertion loss of the patch cord, ILpatch cord, is first estimated as the difference between the measured power and the factory calibrated power.

Light Brigade, Dover Telecommunications join for fiber-optic and wireless training courses

Optical training specialists the Light Brigade,  education and training division, and Dover Telecommunication Services (DTS), a technical and safety training organization for telecommunications professionals, have announced a partnership through which they will provide new instructor-led and online training programs that cover both fiber-optic and wireless applications.

The agreement will see Light Brigade market and sell technical and safety training courses for the wireless industry and DTS market and sell fiber-optic training programs from the Light Brigade.

“Many companies require associates to keep up-to-date on the latest technology and follow certain safety procedures,” said Dario De Paolis, vice president and general manager of the Light Brigade. “By offering extended services to our respective customers, our customers will receive industry-leading, hands-on training for fiber optic and wireless applications and our wireless customers will gain required and highly sought-after skills.”

The courses will provide best practice techniques and hands-on skills training for those involved in the design, planning, installation, maintenance, or troubleshooting of fiber optic and wireless communication networks.

New Fiber Optic Cable with High-Speed Data Transmission

new aerospace fiber optic cable, GORE, which offers a high-speed data transmission cable in a lightweight construction. Designed with a dual-buffering system, GORE delivers signal accuracy for high-speed data transmission in a wide variety of temperature ranges.

With high flexibility, the GORE aerospace fiber optic cable is smaller and lighter weight for improved installation. It includes a tight bend radius for routing in confined spaces of an aircraft. The cable is resistant to crushing, kinking and abrasions and complements GORE’s aerospace product offering including high performance quads, Cat5E, Cat6A, USB3.1, HDMI 2.- and high frequency microwave cables.

Application for the cable includes avionics networks, digital video systems, cabin management systems, flight management systems, Ethernet backbone, transceivers, weather radar systems and inflight entertainment and connectivity systems.

To request more product information, visit W. L. Gore & Associates MRO Links page.

How to Choose OTDR Launch Cable- Connector Type

The primary purpose of using the launch cable is to isolate the ODF connector in order to measure its loss and reflectance. It is therefore VITAL for the selected launch fiber to have the correct ODF termination available. If the network is SC/UPC and your launch fiber is FC/UPC, using a “3 m jumper” to connect to the SC/UPC will result in two connector pairs being measured at the ODF, which is clearly not desirable.

As a result, there may be a need to keep more than one launch fiber in your accessories for the purpose of testing fiber networks. Because most OTDRs have a fixed launch (for example, an SC/APC output), a wide range of SC/APC to xx/xPC cables can be utilized. Another important use of the pulse suppressor/launch lead is to minimize the number of times the OTDR connector is used, ultimately reducing the risk of damage to the OTDR connector and prolonging its service life.

When testing a fiber link without a launch cable, the results will only indicate the reflectance of the first Connector (pair). This causes an issue because the reflectance is associated with two pairs (OTDR and ODF), however the result DOES NOT account for the loss associated with the ODF connection.

Above 90 km, it is common to use 1550 nm/1625 nm in order to permit macrobend detection. If macrobend detection is not required, the current practice is to just use 1550 nm.

Hudson Fiber Network fiber cables Manhattan

Fiber-optic network services provider Hudson Fiber Network (HFN) says it has completed installation of bulk fiber cables throughout Manhattan. HFN says its fiber-optic cables now connect “leading commercial buildings and data centers” throughout New York City.

HFN will use the network infrastructure to offer lit and dark fiber services to data centers including 111 Eighth Avenue, 60 Hudson Street, and 325 Hudson Street. It plans to add the data centers at 375 Pearl Street, 32 Avenue of the Americas, and 85 Tenth Avenue in the future.

“Our new cable allows us to deliver lit and dark fiber services to many commercial buildings that do not yet have fiber or require diverse carrier access,” asserts HFN’s COO, Keith Muller. “The NYC cable connects to our core New Jersey network, providing clients with national and international access connection points at faster speeds with greater bandwidth.”

HFN offers Gigabit Ethernet, optical wavelength, and IP connectivity primarily to financial, content, carrier and enterprise clients. Its network more than 50 commercial buildings throughout New York City in addition to the new Manhattan connections. It says it can connect customers with an average of 60- to 90-day installation time.

Peachtree City approves fiber optic plan

Peachtree City’s city council approved a resolution Thursday to establish a municipal fiber optic broadband utility for local government and commercial use.

The city will work with Community Broadband LLC to finalize business and infrastructure plans, expecting to have the first customers online within a year. The city will initially use a $3.2 million bond to finance the project. Financial Services Director Paul Salvatore said the city would benefit from having its own “backbone” to use and lease.

The high-speed system would be marketed to existing and new businesses, but service to residential customers is unlikely because of the additional lines required and competition with existing cable TV providers.

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