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When purchasing fiber transceivers, transmission distance is often represented by various letter abbreviations. What do they mean? How do we distinguish them? Below, we will explain them one by one for you.
In fiber transceiver terminology, abbreviations such as SR, DR, FR, LR, ER, and ZR respectively represent different transmission distance and rate categories.
SR = Short Reach
SR stands for Short-Range Transmission, designed for short distances. It operates at a wavelength of 850nm and is paired with multimode fiber, enabling transmission distances within 300 meters. It is suitable for interconnecting equipment within a data center.
SFP-10G-SR Fiber Transceiver
LC LC Duplex Patch Cord OM3
DR=Data Center Reach
DR (Digital Transmission) is designed for short-distance transmission over 500 meters using single-mode fiber at a wavelength of 1310nm. Data rates are typically 25Gbps or higher per channel, meeting the needs of high-performance short-distance data transmission, switch interconnection, server and storage connections, and other similar scenarios.
FR=Fiber Reach
FR is for medium-range transmission. It is a single-mode fiber transceiver with a wavelength of CWDM4 and a maximum transmission distance of 2km. It is commonly used for medium-range data communication.
LR=Long Reach
LR stands for long transmission distance, using a 1310nm wavelength. Single-mode fiber transmission can reach 10km and is commonly used in campus networks and local area network cabling.
SFP-10G-LR Fiber Transceiver
LC LC Simplex Patch Cord
LRM fiber transceiver can transmit up to 200 meters in multimode fiber, making it suitable for short-distance LAN connections. Upgraded versions can reach up to 2km.
ER=Extended Reach
ER is an ultra-long-distance fiber transceiver for 40km transmission by single-mode fiber. It uses 1550nm or 1310nm wavelengths and commonly used for data center interconnection.
QSFP-40G-ER Fiber Transceiver
LC LC Duplex Single Mode Patch Cord
ZR=ZeRo Dispersion Reach
ZR is very long-distance transmission, typically refers to single-mode fiber (SMF) transmission over distances of 80 kilometers or more, primarily used for fiber optic communication to reduce dispersion effects. It employs a 1310nm wavelength and is used in long-distance backbone networks.
SFP-10G-ZR100 Fiber Transceiver
LC LC Duplex Single Mode Patch Cord
Conclusion
According to you needs, for short distances, select SR transceiver; for medium distances, select LR transceiver; for long distances, select ER transceiver or ZR transceiver.
| Transceiver type | Working wavelength | Fiber typoe | Transmission distance | Typical application |
| SR | 850nm | Multimode fiber | 300m | Intra-data center equipment interconnection (servers, switches) |
| DR | Single mode short distance, 1310nm | Single mode fiber | 500m | High-density data center rack interconnection |
| FR | CWDM (including 1281nm, 1291nm, 1311nm, 1331nm, etc) | Single mode fiber | Max. 2km | Inter-building interconnection of data centers within the same campus |
| LRM | Multimode short distance | Multimode fiber | 220m, upgrade 2km | Enterprise LAN equipment connectivity |
| LR | 1310nm | Single mode fiber | 10km | Campus network and metropolitan area network cabling |
| ER | 1550nm or 1310nm | Single mode fiber | 40km | Interconnection of data centers across urban and suburban areas, medium- and long-distance metropolitan area networks |
| ZR | 1310nm | Single mode fiber | 80km | Intercity and interregional backbone network transmission |
How to calculate the transmission distance of a fiber transceiver?
There are three factors in calculating the transmission distance of a fiber transceiver:
- 1. Transmit optical power at the transmitter
- 2. Receiver sensitivity at the receiver
- 3. Optical attenuation coefficient of the wavelength
Assuming the optical module’s transmit optical power is -4dB and the receiver sensitivity is -22dB, we use -4 – (-22) = 18dBm, meaning the fiber transceiver can accept 18dBm of fiber loss.
With a wavelength of 1310nm and an optical attenuation coefficient of 0.35dBm/km, the calculation formula is:
18dB/(0.35dB/km) = 51.428km
In other words, considering only fiber loss, the maximum transmission distance is 51km.
FAQ
What is DR?
In fiber transceiver, DR is usually an abbreviation for Data Rate, refers to the transmission type of Data Center Reach. It represents a medium-to-short distance, single-mode fiber (SMF) based transmission solution, with a distance of around 500 meters, used for internal or regional connections within data centers.
What are SR4, LR4, and ER4?
SR4, LR5, and ER4 are abbreviations for the transmission distance of 100G QSFP28 fiber transceiver. QSFP28 is a 100G fiber transceiver using an small form pluggable package. The “4” indicates that it has four channels, each with a maximum transmission rate of 28Gbps. QSFP28 100G LR4 means that this 100G long-distance module can transmit 100G signals using four wavelengths, with a maximum distance of up to 10km.
We will be building a data center in this campus. What fiber transceiver type should we use?
For a large campus, we recommend choosing an LR 10km transmission optical module.
