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How to Measure the Performance Indicators of Optical Modules?

Posted on Feb 2, 2024 by
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Optical modules, including the advanced 25G SFP28 transceiver, play a pivotal role in modern communication systems, facilitating the transmission of optical signals. Assessing the performance of these modules is crucial to ensuring their reliability and efficiency in various applications. This article provides a comprehensive guide on measuring key performance indicators to evaluate the functionality of optical modules, with a specific focus on the sfp28 transceivers.

The Working Principle of an Optical Module

A comprehensive understanding of the working principle of an optical module is essential for determining the relevant performance indicators to measure, ensuring that the module functions optimally in a given optical communication system.

The working principle of an optical module involves the transmission and reception of optical signals, and it typically consists of a transmitter and a receiver.

Transmitter:

The transmitter component of an optical module is responsible for converting electrical signals into optical signals for transmission over optical fibers. The key steps in the transmitter's operation include:

  • Electrical-to-Optical Conversion: The input electrical signals, typically in the form of data or communication signals, undergo modulation to impart the information onto an optical carrier signal.

  • Laser Emission: The modulated electrical signals drive a laser diode within the transmitter. The laser diode emits coherent light corresponding to the modulated electrical signals, transforming them into optical signals.

  • Optical Signal Launch: The emitted optical signals, now carrying the encoded information, are coupled into optical fibers for transmission over the communication network.

Receiver:

On the receiving end, the optical signals are converted back into electrical signals. The receiver component of the optical module executes the following essential steps:

  • Optical Signal Reception: Optical signals arriving from the optical fibers are directed to a photodiode within the receiver.

  • Photodetection: The photodiode converts the received optical signals into electrical currents. The incident light generates electron-hole pairs in the semiconductor material of the photodiode, resulting in a current proportional to the received optical power.

  • Electrical-to-Optical Conversion (Optional): In some cases, the electrical signals may be further processed or converted back to optical signals for onward transmission through the optical module.

  • Signal Processing: The electrical signals are processed to retrieve the original data or communication content.

By seamlessly integrating the functions of electrical-to-optical and optical-to-electrical conversion, optical modules enable the efficient and high-speed transmission of data across optical communication networks. The coordinated operation of the transmitter and receiver ensures reliable and accurate communication in diverse applications, ranging from telecommunications to data centers.

FS has different kinds of optical modules, but the figure below fully demonstrates the working principle of the FS 25G module, FS 25G SFP28 Transceiver exhibits superior performance across various parameters, ensuring its suitability for diverse applications and requirements. These modules are qualified through a rigorous process with advanced equipment to ensure you get high-quality and reliable optics.

A comprehensive understanding of the working principle of an optical module is essential for determining the relevant performance indicators to measure, ensuring that the module functions optimally in a given optical communication system.

How to Measure the Performance Indicators of Optical Modules?

Optoelectronic devices have two parts: transmitting and receiving. The performance indicators for measuring optical modules are also divided into two categories: Transmitter End and Receiver End. Measuring the performance indicators of optical modules involves using specific tools and techniques to assess various parameters on the transmitter and receiver sides. Here's a summary of how to measure the key performance indicators of optical modules.

Optical Module Transmitter Side:

Average Transmit Optical Power:

  • Measure the optical power output of the transmitter under normal operating conditions.

  • Express the result in units such as Watts (W), milliwatts (mW), or decibels milliwatts (dBm).

Extinction Ratio:

  • Determine the minimum value of the average optical power for full "1" code and the average optical power for full "0" code.

  • Calculate the extinction ratio in decibels (dB).

Center Wavelength of the Optical Signal:

  • Identify the wavelength corresponding to the midpoint of the line segment connecting 50% of the maximum amplitude in the emission spectrum.

  • Typically, optical modules operate in common bands such as 850nm, 1310nm, and 1550nm.

Receiving Side of Optical Module:

Overload Optical Power:

  • Measure the maximum input average optical power that the receiver can handle under specific conditions (e.g., BER = 10^-12).

  • Express the result in dBm.

Receiving Sensitivity:

  • Determine the minimum average input optical power that the receiver can reliably detect under a specific BER condition (e.g., BER = 10^-12).

  • Express the result in dBm.

Receive Optical Power:

  • Measure the average optical power received by the receiver component within a certain BER condition.

  • Express the result in dBm, with the upper limit being the overload optical power and the lower limit being the receiving sensitivity.

Comprehensive Performance Indicators:

Interface Rate:

    • Check the maximum electrical signal rate that the optical module can carry without error code transmission.

    • Follow the specified rates in Ethernet standards, such as 125Mbit/s, 1.25Gbit/s, 10.3125Gbit/s, 41.25Gbit/s.

Transmission Distance:

      • Assess the maximum distance the optical module can transmit signals, considering factors like fiber loss and dispersion./p>

      • Loss is due to energy dissipation, and dispersion is the spreading of pulses over distance.

Optical Module Type:

      • Specifies the type of optical module based on its design and intended use (e.g., SR, LR, ER).

      • Determines the module's suitability for different network scenarios.

General Approach to Measurement:

      • Utilize specialized equipment such as optical power meters, optical spectrum analyzers, and bit error rate (BER) testers.

      • Perform tests under standard conditions to ensure consistency and comparability.

      • Adhere to industry standards and specifications for optical module performance testing.

By systematically measuring these parameters using appropriate tools and methods, one can evaluate and ensure the optimal performance of optical modules in various networking applications.

By systematically measuring these parameters using appropriate tools and methods, one can evaluate and ensure the optimal performance of optical modules in various networking applications.

Factors Affecting the Performance of Optical Modules

The performance of optical modules is influenced by various factors. Here are some key factors that can affect their performance:

      • Optical Signal Quality: The quality of the optical signal, including factors such as signal-to-noise ratio (SNR) and signal integrity, plays a crucial role in the performance of optical modules. Any degradation in signal quality can impact data transmission.

      • Connector Quality: The connectors used in optical modules should be of high quality to ensure reliable connections. Poorly maintained or damaged connectors can lead to signal loss, affecting performance.

      • Fiber Quality and Length: The quality and length of the optical fiber used in the module can impact signal attenuation and dispersion. High-quality fiber with proper length specifications is essential for optimal performance.

      • Temperature Stability: Optical modules are sensitive to temperature variations. Fluctuations in temperature can lead to changes in the refractive index of the optical components, affecting signal propagation. Therefore, maintaining temperature stability is critical.

      • Wavelength Stability: Optical modules often operate at specific wavelengths. Any instability in the wavelength can affect the transmission characteristics. Stable and precise wavelength control is important for reliable performance.

      • Environmental Conditions: The operating environment, including factors like humidity and dust, can affect the performance of optical modules. Proper environmental controls and protection are necessary to prevent damage and signal degradation.

      • Power Levels and Budget: Ensuring that the optical power levels are within specified ranges and that the power budget is maintained is crucial for reliable performance. Deviations from recommended power levels can impact signal quality.

Addressing and optimizing these factors is essential for maintaining the high-performance levels expected from optical modules in various communication and networking applications.

Addressing and optimizing these factors is essential for maintaining the high-performance levels expected from optical modules in various communication and networking applications.

Conclusion

In conclusion, With a specific focus on the 25G SFP28 transceiver, we know that optical modules play a vital role in modern communication, facilitating the conversion of electrical signals to optical signals (transmitter) and vice versa (receiver). The exceptional versatility, stability, adaptability, and high-bandwidth support of FS 25g sfp28 transceivers make them an ideal and comprehensive solution for meeting diverse communication requirements. If we better understand the working principle of optical modules and how to measure the performance of optical modules, we can help us ensure the best performance of optical modules in various network applications.

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