What is the extinction ratio of transmission?

Extinction Ratio of Transmission

The extinction ratio (ER) in optics refers to the ratio of the power transmitted when light is passing through a polarizer (or an optical modulator) in its transmitting state to the power transmitted when it is in its blocking state. It is a parameter of paramount importance in fiber optics and telecommunication systems, particularly in systems utilizing optical modulators to encode digital signals onto light for transmission through an optical fiber.

The extinction ratio is commonly represented by the equation:
ER = P_on / P_off,
where P_on is the optical power level when the device is in the 'on' state (transmitting light), and P_off is the optical power when the device is in the 'off' state (blocking the light).

Importance of a High Extinction Ratio

• A higher extinction ratio indicates better performance of optical components, such as modulators or switches, as it reflects a greater distinction between the 'on' and 'off' states.
• In digital communication systems, a higher ER leads to enhanced signal integrity and reduced bit error rates, as it helps to clearly differentiate between logic levels '1' (light) and '0' (no light).

The extinction ratio is typically measured in decibels (dB) and can also be expressed as ER(dB) = 10 * log10(P_on / P_off).

Overall, the extinction ratio is a critical specification for components in optical networks where precise control over light is essential. It is one of the key parameters used to evaluate the performance of polarizers, optical modulators, and related devices in transmitting digital information.