RM3 SERIES BACKREFLECTION METER

USER’S MANUAL

Backreflection Measurements

Reflections in optical systems can come from a number of sources. Primary sources include the fiber (Rayleigh backscatter) and Fresnel reflections that occur at the planar junction of two materials having different refractive indices, for example, connector and fiber endfaces, splices, bulk optic interfaces, and detector surfaces.

Typically only Fresnel reflections are significant because transmitters are relatively insensitive to distributed reflections such as Rayleigh backscatter. Backreflection caused by Rayleigh backscatter varies with the length and type of fiber, and is only significant when measuring components with backreflections below -40 dB or with very long pigtails (multimode). However, Rayleigh backscatter can be a large contributor to backreflection in installed systems or when using long fiber.

The internal switch and coupler of the RM meter enable the meter to measure the internal light source signal (Pin), the signal offset with no light (Pdark), and the total signal level from internal and external backreflections (Pbr).

The RM meter first calculates the total backreflection from internal and external sources (BRtot), using the following equation, where CAL is the factory-set calibration factor of the meter:

BRtot = 10 log (Pbr - Pdark)/(Pin - Pdark) - CAL

[dB]

The backreflection from external sources (BR) is then calculated using the following equation, where BR0 is the stored value of the total backreflection up to the device under test (DUT), and User CAL is the user-set calibration factor:

BR = 10 log (10BRtot/10 - 10 BR0/10) + User CAL

[dB]

The RM meter then displays the value of BR.

The BR measurement takes approximately one second to complete. Before this is done, the Pin and Pdark measurements are completed in approximately four seconds, during which time the backreflection display is locked and the light from the output port is blocked. The values are then updated every minute.

Loss and Power Measurements

The RM meter is equipped with a front-panel InGaAs detector for relative power (loss) and absolute power measurements. (Absolute power is referred to as power in this manual; relative power is always referred to as relative power.) Because the meter is capable of storing the dark signal from the detector, high-accuracy power measurements as low as -80 dBm for the single mode model (and –60 dBm for the multimode model) can be obtained.

When making power measurements, the RM meter first measures two signals: the total signal level (Itot) and the dark signal from the detector (ID). The RM meter then calculates the power measurement using the following equation, where CAL is the factory-set calibration factor and User CAL is the user-set calibration factor:

P = 10 log (Itot - ID) + CAL + User CAL

[dB]

 

 

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JDS Uniphase RM3750 user manual Backreflection Measurements, Loss and Power Measurements
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RM3750 specifications

The JDS Uniphase RM3750 is a cutting-edge optical spectrum analyzer that has garnered attention in various telecommunications and photonics applications. Renowned for its versatility and accuracy, the RM3750 combines advanced technologies to provide users with unprecedented measurement capabilities, making it an essential tool for researchers and engineers working in fiber optics, laser development, and spectral analysis.

One of the standout features of the RM3750 is its wide dynamic range. This feature allows users to obtain precise measurements across a broad spectrum of optical signals, which is crucial in environments where signal strength can vary significantly. The analyzer is designed to handle both high-intensity signals and weak optical events, ensuring that no detail is missed during analysis.

The RM3750 incorporates a high-resolution detection mechanism that enables it to distinguish closely spaced wavelengths. This characteristic is particularly beneficial in applications where wavelength spacing is minimal, such as in dense wavelength division multiplexing (DWDM) systems. The high resolution also allows for accurate characterization of spectral features, including signal peaks and noise.

In addition to its impressive measurement capabilities, the RM3750 supports advanced analysis and real-time monitoring. Users can visualize spectral data through an intuitive graphical interface, which aids in the quick interpretation of results. The instrument is equipped with real-time data processing capabilities, allowing users to observe changes in optical signals as they occur, a critical feature for dynamic environments like live signal monitoring.

The JDS Uniphase RM3750 is not only about hardware; it also comes with an array of software tools designed to enhance functionality and ease of use. These tools allow for automated measurements, data logging, and integration with other laboratory instruments. Moreover, the ability to export data in various formats facilitates easy sharing and analysis across platforms.

Another notable characteristic of the RM3750 is its compact design and robust build quality. This ensures that it can operate effectively in demanding laboratory conditions while being portable enough for field applications.

In conclusion, the JDS Uniphase RM3750 optical spectrum analyzer stands out for its combinations of wide dynamic range, high resolution, real-time monitoring, and user-friendly software integration. These characteristics make it an exceptional tool for professionals in telecommunications and optical research, enabling them to conduct more accurate and insightful measurements.
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