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Three Factors for Choosing an OTDR Optical Time Domain Reflectometer

Date: 07, April, 2022
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Ⅰ. Determine your OTDR system parameters


Grandway OTDR test series include FHO 1000 handheld series, FHO 3000 mini series, FHO 5000 series, etc. To meet the challenges of various optical network testing, Grandway offers a wide range of OTDR options. FHO 1000 Handheld OTDR is the latest smart OTDR from Grandway. Although it is a handheld OTDR, it can measure fiber lengths over 100 kilometers. In short-distance fiber testing, with excellent 1m/4m dead zone performance, various events such as continuous connectors, attenuation loss, etc. can be clearly distinguished.


Ⅱ. Clarify your OTDR working environment


For users and buyers, when choosing a field instrument, the temperature standard may be the most stringent: usually, field measurements must be carried out in severe environments. It is recommended that the working temperature of field portable instruments should be from -18℃ to 50℃, and the storage and transportation temperature is -40~ to 60℃ (95%RH). Laboratory instruments only need to work within a narrow control range of 5°C to 50°C. Handheld OTDR is used for on-site opening, acceptance, and maintenance testing of optical fiber communication systems. The working temperature is -10°C to 50°C, and the storage and transportation temperature is -40°C to +60°C, which is completely suitable for the site.


Unlike laboratory instruments that can be powered by AC, field portable instruments usually have stricter requirements on instrument power, otherwise it will affect work efficiency; in addition, the power supply problem of instruments is often an important cause of instrument failure or damage. The Grandway handheld OTDR uses a lithium rechargeable battery with an AC charger, which solves the problem of power supply.


Ⅲ. OTDR comparative performance factors


1. Dynamic range


This index determines the maximum optical loss value that the OTDR optical time domain reflectometer can analyze; that is, it determines the maximum fiber length that the OTDR can measure. The greater the dynamic range, the farther the distance OTDR can analyze. Dynamic range is an index that must be considered very carefully, mainly for two reasons:


OTDR manufacturers may use different methods to identify dynamic range (such as pulse width, signal-to-noise ratio, averaging time, etc. defined by the index). Therefore, it is necessary to have a deep understanding of this index, so as to avoid errors due to different premise and objects when comparing different instruments.


If the dynamic range of the OTDR is not large enough, the length of the entire link cannot be tested, and in many cases, it will affect the test accuracy of the entire link loss, attenuation, and remote connector. One rule of thumb is to choose the actual dynamic range value of the OTDR, which should be 5 to 8 dB higher than the maximum loss it might encounter.


2. Dead zone (attenuation dead zone and event dead zone)


When evaluating the performance of an OTDR, the dead zone is a very important index that determines whether an accurate test can be performed on the entire link. There are generally two types of dead zones:


Event dead zone: this index refers to the minimum distance between two reflection events that the OTDR can distinguish. That is, the ability to distinguish two events. If a reflection event is in the dead zone of its previous event, the event cannot be detected or properly tested. The industry standard value is 1 meter to 5 meters.


Attenuation dead zone: this index refers to the distance after a reflection event, after which the OTDR can accurately test the loss of another reflection event or non-reflection event. A short dead zone OTDR can test a short distance fiber or can find the failure of a short optical jump line, the shorter the dead zone, the better the effect. In industry standards, this index is generally between 3 meters and 10 meters.


3. Linearity


Linearity refers to the OTDR's ability to suppress noise. The linearity of the instrument is very important because it is directly related to the accuracy of the loss test of the fiber, such as the accurate test of the loss caused by the splice or fiber macrobend. In industry standards, the linearity index is between 0.03dB/dB and 0.05dB/dB.


4. Sampling resolution


Sampling Resolution: sampling resolution refers to the minimum distance between two adjacent sampling points. This parameter is also an important parameter, which can affect the test distance accuracy and the ability of the OTDR optical time domain reflectometer to determine the fault point. This parameter is related to pulse width and distance.

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