Overview
QSFP28 optical transceivers are becoming increasingly popular due to their smaller size, lower power consumption, and higher density over CFP (Recommended to read: CFP vs. QSFP28 100G, What’s the Difference?) and higher data rate over SFP (ie. QSFP-100G-SR4-S supports 100 Gbit/s while SFP-10G-SR supports 10 Gbit/s). Their transmission distance ranges from 100m to 100km. In this article, we will point out the differences between QSFP28 ER4 40KM APD and SOA solutions from the definition, technology, and application aspects.
What is the 100GBASE ER4 Standard?
Before understanding the definition of 100G ER4 optical transceiver, I would like to introduce the 100Gbase ER4 standard 100Gbase ER4 optical module standard is defined by IEEE 802.3ba, which supports dense wavelength division multiplexing (DWDM) technology and transmits signals over single-mode fiber optic cables operating at a wavelength of 1310nm. IEEE also defines ” ER” is defined as an extended range. But how does the QSFP28 ER4 extend the transmission range? Extending the range is using a semiconductor optical amplifier (SOA) that amplifies the optical signal before it enters the PIN photodetector.
What are 100GBASE ER4 Applications?
The 100G ER4 module is the best choice for long-distance transmission up to 40km. It can be used for 100G direct connect and interconnect for enterprise networks and data centers.
When comparing 100G 40KM APD (Avalanche Photodiode) and SOA (Semiconductor Optical Amplifier) solutions, there are some critical differences in terms of technology, performance, and application. The following is a detailed description:
Technology
APD (Avalanche Photodiode)
Function: Used to detect optical signals.
Principle of operation: Amplification of incident light through the avalanche process to increase sensitivity.
Advantages: Higher sensitivity and better performance in low light conditions.
SOA (semiconductor optical amplifier)
Function: Used to amplify optical signals: Used to amplify optical signals.
Operation: Directly amplifies optical signals without first converting them to electrical signals.
Advantages: Provides gain for long-distance signals and can be integrated into photonic circuits.
Performance
APD
Sensitivity: Higher sensitivity at lower power.
Speed: Generally better in 100G applications.
Noise: More susceptible to noise, especially at higher gains.
SOA
Gain: Provides significant optical gain for long-distance transmission.
Linearity: Linearity is generally good and helps maintain signal integrity over long distances.
Noise Figure: Typically lower than APDs at large signal levels.
Applications
APD
Use Case: Ideal for applications requiring high sensitivity, such as metro networks and short-distance links.
Deployment: Typically used as receivers in optical communication systems.
SOA
Use Case: Commonly used as a booster in long-haul optical networks and optical communication systems.
Deployment: Suitable for applications that require amplification of signals without conversion to electrical signals.
Cost and Complexity
APD
Cost: This can be expensive due to additional bias and noise management circuitry.
Complexity: Requires careful handling of noise and sensitivity adjustments.
SOA
Cost: Typically lower for bulk amplification applications but adds complexity to integration.
Complexity: Easier to integrate into existing optical networks but may require precise control mechanisms.
| 6C-QSFP28-ER4-APD | |
| QSFP28 1295-1310nm 40KM，EML/SOA PIN | QSFP28 1295-1310nm 40KM, EML/APD |
Summary
APD solutions are suited for high-sensitivity and short-range applications, while SOA solutions are suited for long-range signal amplification and maintaining signal integrity. The choice between the two depends on the specific requirements of the optical communication system being designed.