QSFP28 100Gbase LR1 Transceiver

The QSFP28 100Gbase LR1 transceiver is a high-performance, medium to long distance transmission (10km) high-density optical module based on Single Lambda technology. It adopts QSFP28 packaging and achieves 100Gbps transmission on single-mode fiber through 1310nm wavelength. It simplifies the internal design by converting the four 25G channels on the electrical side into a single 100G signal on the optical side, making it an economical choice for data center interconnect (DCI) and 5G carrier network.

100G LR1 Optics Specifications

Model	QSFP28-100G-LR1
Package type	QSFP28 (same packaging as 100G SR4/LR4)
transmission rate	106.25Gbps (1 x 53.125GBd PAM4), effective data rate 100G
Optical interface type	Duplex LC
Fiber type	Single mode fiber (SMF, G.652)
Transmission distance	10 kilometers (standard)/20 kilometers (enhanced version, FEC needs to be enabled)
Working wavelength	1310nm (single wavelength)
Emitter type	EML (Electro Absorption Modulation Laser) or Silicon Optical Scheme
Receiver type	PIN photodiode
Power consumption	<4-4.5W (typical 3.5-4.5W)
Operating Temperature	Commercial grade 0 ℃ to 70 ℃
Electrical interface	CAUI-4（4 x 25.78Gbps NRZ）
Protocol standard	IEEE 802.3cu 100GBASE-LR1、100G Lambda MSA、QSFP28 MSA

Single wavelength 100G PAM4:

• QSFP28 100Gbase LR1 adopt PAM4 (4-stage pulse amplitude modulation) technology with a single channel symbol rate of 53.125GBd
• Compared to traditional 4 × 25G NRZ schemes (such as LR4 100G), the number of optical devices is reduced by 75%, resulting in lower costs and better power consumption

100G LR1 FEC requirements:

• KP-FEC (Forward Error Correction) needs to be enabled for 10 km transmission to ensure bit error rate performance
• FEC can correct bit errors in transmission and is the key to achieving 10km transmission with a single wavelength 100G scheme

Power consumption performance:

• 100G LR1 SFP typical power consumption<4W, some optimized products can reach<3.5W
• Compared to the traditional 100G QSFP28 LR4 (10 km, 4 wavelengths) scheme, the power consumption of 100G QSFP28-LR1 is comparable or slightly lower, but the cost advantage is obvious

Electrical interface:

• The host side of LR1 adopts CAUI-4 interface: 4-channel 25.78Gbps NRZ signal
• Internally, the LR1 transceiver module converts 4 × 25G NRZ to 1 × 100G PAM4 using Gearbox DSP

Technical architecture and working principle

Core Architecture: 4 x 25G NRZ ↔ 1x100G PAM4

The core of 100Gbase LR1 is the Gearbox DSP chip inside the transceiver, which completes the rate conversion between the electrical interface and the optical interface:

Two main technologies

Technology	Features
EML scheme	Traditional mature technology, stable performance, using refrigerated EML laser, supporting 10-20km
Silicon Light Solution	High integration, controllable cost, suitable for large-scale deployment, also supports 10km

Silicon photonics technology integrates optical and electronic components on a single chip, demonstrating cost advantages in large-scale deployment scenarios such as AI data centers.

Single Lambda 100G DR1 LR1 FR1

The 100G QSFP28 LR1 is a long-distance transceiver designed for 100G Ethernet interconnection within 10 km of data centers and campus networks, using single wavelength 100G PAM4 technology. It belongs to the single wavelength 100G product family along with DR1 (500 m) and FR1 (2 km), and LR1 is the model with the longest transmission distance in this series. Below are the specific differences between the following three models:

Item	100G DR1	100G FR1	100G LR1
transmission distance	500 m	2 km	10 km( 20km optional）
core technology	1×100G PAM4	1×100G PAM4	1×100G PAM4
interface type	Duplex LC	Duplex LC	Duplex LC
Fiber optic type	single-mode fiber	single-mode fiber	single-mode fiber
transmitter	EML/Silicon optics	EML/Silicon optics	EML（enhanced）
FEC requirements	KP-FEC	KP-FEC	KP-FEC
power consumption	<4W	<4.5W	<4-4.5W
protocol standard	IEEE 802.3cu 100GBASE-DR1	IEEE 802.3cu 100GBASE-FR1	IEEE 802.3cu 100GBASE-LR1

Difference 100G LR1 vs LR4

Although both 100G LR1 and LR4 can run 10 km, the core of LR1 lies in its “single wavelength”, which significantly reduces the number of optical components, lowers fault points, and production costs. LR4, on the other hand, has four parallel wavelengths and a significantly different internal structure.

Item	100G LR1（single wave）	100G LR4（4 wavelengths）
Technical Architecture	1×100G PAM4	4×25G NRZ + WDM
Number of wavelengths	1 (1310nm)	4 (LAN-WDM, approximately 1295-1310nm)
Number of optical components	1 EML	4 DFB/EML+AUX/DEMUX
internal components	Integrated DSP chip for signal processing	No need for complex DSP processing
interface type	Duplex LC	Duplex LC
Number of optical fibers	2-core	2-core
transmission distance	10 kilometers (optional 20km)	10 kilometers
power consumption	<4W	<4.5W
cost	Lower (fewer components)	higher
FEC requirements	Need KP-FEC	No need
Interoperability	Incompatible (the two cannot communicate directly)	incompatible
Applicable scenarios	New network, cost sensitive	Compatibility with existing networks

Selection suggestion:

• New data center/campus network → LR1 (lower cost, more advanced technology)
• Need to be compatible with existing LR4 infrastructure → LR4 (no need to modify the peer device)

BiDi LR1 – Bidirectional transceiver

In addition to the standard dual fiber LR1 (one transmitter, one receiver, using 2-core fiber), there is also a BiDi LR1 (single fiber bidirectional) version, This transceiver bidi needs to be used in pairs.

Model	QSFP28-100G-BIDI-10
Technical Principle	Using two different wavelengths (1271nm and 1331nm) to simultaneously transmit and receive on one optical fiber
interface type	Single LC (1-core fiber)
transmission distance	10 kilometers
Paired use	Must be paired, with one end using TX1271/RX1331 and the other end using TX1331/RX1271
Applicable scenarios	In scenarios where fiber optic resources are extremely scarce, save 50% fiber optic

100G QSFP28-LR1 Applications

Data Center Interconnection (DCI)

100G LR1 is an ideal solution for 10 km interconnection between data centers:

• Scenario: Main Data Center and Disaster Recovery Center, Same City Dual Active Data Center
• Distance: 10 km, covering most of the same city DCI requirements
• Advantages: Single mode fiber+duplex LC, 2 cores are sufficient, and the cost is better than traditional LR4

Core interconnection of park network

For 100G core links between different buildings in large parks

• Scenario: University Park, Science and Technology Park, Corporate Headquarters Park
• Distance: 2-10 kilometers, sufficient LR1 distance
• Value: The cost of a single wave rectangular plan is controllable, making it the preferred choice for upgrading the park to 100G

Metropolitan area access/aggregation

In the telecommunications metropolitan area network, 100G LR1 can be used for long-distance interconnection between the access layer and the aggregation layer:

• Scenario: 100G link between stations
• Distance: 10 km, covering urban edge scenes
• 20km version: 20km version is available, suitable for longer distances

400G DR4 Breakout

100Gbase LR1 (replacing 100G DR1) is used in conjunction with 400G DR4 to achieve 1 to 4 breakout:

• 400G DR4 MPO module: 4 × 100G parallel, MPO-12 interface
• Branch scheme: 400G DR4+MPO-12 to 4 x LC breakout cable → 4 units of 100G LR1 equipment
• Value: 1pc 400G port can serve 4 x 100G devices, flexible expansion

How to choose the appropriate 100G QSFP28 LR1 version?

Scenario requirements	Recommended Solution	Reason
Data center interconnection (≤ 10km)	100G LR1	Single wavelength technology, lower cost than LR4, 2-core single-mode fiber
Data Center Interconnection (10-20km)	100G LR1 20km version	20km enhanced version optional
Core interconnection of the park (2-10km)	100G LR1	Adequate distance, power consumption<4W, high cost-effectiveness
Fiber optic resources are extremely scarce	100G BiDi LR1	Single fiber bidirectional, saving 50% fiber, needs to be used in pairs
Must be compatible with existing LR4 devices	100G LR4	LR1 and LR4 have different wavelength schemes and cannot directly communicate with each other
Pursuing the lowest power consumption	Low power version LR1 (<3.5W)	For example, CIOE exhibitors provide optimized versions

Conclusion

The 100G QSFP28 LR1 is a single wavelength rectangular scheme for 10 km long-distance interconnection, using 1 × 100G PAM4 technology and 1310nm EML laser. It achieves 10 km (optional 20 km) transmission on single-mode fiber through duplex LC interface, with a power consumption of less than 4.5W.

Compared with the traditional 4-wavelength LR4, LR1 has become a new generation standard solution for 100G long-distance interconnection with a simpler architecture and lower cost.

For scenarios where fiber optic resources are extremely scarce, the BiDi LR1 version can also be used to achieve bidirectional transmission over a single fiber.