♦ Introduction
In optical communication, performance depends not only on average launch power or wavelength stability but also on the clarity of the optical signal itself. One of the most important parameters that determines this clarity is the Extinction Ratio (ER). The Extinction Ratio defines how distinct the “on” (logic 1) and “off” (logic 0) states of an optical transmitter are, making it a direct indicator of signal quality in optical transceivers.
♦ What is the Extinction Ratio (ER)?
Extinction Ratio (ER) is the ratio of the optical power when the transmitter is in the logic 1 state (P₁) to the optical power when it is in the logic 0 state (P₀):
Higher ER: Stronger contrast between “on” and “off,” making signals easier to detect.
Lower ER: Weak contrast, leading to difficulties in distinguishing bits.
♦ Why ER Matters in Optical Modules
1. Receiver Sensitivity
A high ER improves the receiver’s ability to distinguish between logic states, directly impacting receiver sensitivity. A poor ER means a smaller optical modulation amplitude (OMA), which makes it harder for the receiver to interpret the incoming data correctly.
2. Bit Error Rate (BER)
Low ER increases the chance of bit misinterpretation, leading to higher BER. A sufficient ER helps ensure error-free transmission across long distances or high-speed links.
3. System Reliability
In modern networks, where optical modules are used for 10G, 25G, 100G, or even 400G Ethernet, maintaining an adequate ER is critical for long-term system reliability and performance stability.
♦ Typical Extinction Ratio (ER) Requirements
Optical Module Type | ER Requirement | Standard Reference |
|---|---|---|
10GBASE-LR (SMF, 10km) | ≥ 3.5 dB | IEEE 802.3ae |
10GBASE-ER (SMF, 40km) | ≥ 4.0 dB | IEEE 802.3ae |
10G DWDM / ZR (SMF, ~80km) | ≥ 8.2 dB | ITU-T G.959.1 / MSA |
25G / 100G / 400G PAM4 modules | Outer ER specified (≈ 3.5–4 dB typical) | IEEE 802.3bm/bs/cd |
📌 Note
At LINK-PP, all optical transceivers are manufactured and tested in compliance with IEEE and ITU standards. Parameters such as Extinction Ratio (ER), OMA, and sensitivity are strictly verified and clearly indicated in the product datasheets and drawings.
♦ Measuring and Interpreting ER
ER is usually measured with an oscilloscope while the laser is transmitting data at the rated speed. The measured value is compared with the minimum requirement in the module datasheet. It’s important to interpret ER together with average power and OMA, since these parameters work together to define overall transceiver performance.
♦ Extinction Ratio in LINK-PP Optical Modules
LINK-PP offers a wide range of SFP modules designed to meet international standards such as IEEE 802.3. Each module datasheet specifies minimum ER values, ensuring compatibility with demanding applications in data centers, 5G networks, and telecom infrastructure.
For example:
Short-reach SFP modules balance ER and power for cost-effective, high-performance LAN applications.
Long-haul DWDM modules maintain higher ER values to preserve signal integrity across multiplexed channels.
♦ Conclusion
The Extinction Ratio (ER) is more than just a specification on a datasheet—it is a critical performance metric that affects receiver sensitivity, bit error rate, and overall system reliability. When selecting an optical module, engineers should consider ER alongside average launch power, OMA, and receiver sensitivity to ensure robust network performance.
With LINK-PP optical modules, customers can count on reliable ER values that meet or exceed industry standards, helping maintain error-free communication in high-speed and mission-critical networks.
