What is LWDM? A Simple Guide in 2025

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Maybe you have heard about CWDM and DWDM technology and used CWDM and DWDM Products, but do you know LWDM(LAN WDM)? Is it a little strange for you? If so, you have found the right place to learn it. This blog will include the info you want about LWDM.

What is LWDM?

LWDM is short of LAN WDM (Local Area Network Wavelength Division Multiplexing). It is a type of WDM (Wavelength Division Multiplexing) technology that can transmit multiple data over a single fiber using different wavelengths.

LAN WDM typically operates in the O-band of the optical spectrum(1260nm-1360 nm), which is the original band with very small dispersion. Optical components such as lasers, detectors, and filters are typically designed to operate within the O-band, which makes it an optimal choice for efficient and cost-effective LWDM systems. IEE has assigned 12 channels for LAN WDM(1269.23, 1273.54, 1277.89, 1282.26, 1286.66, 1291.1, 1295.56, 1300.05, 1304.58, 1309.14, 1313.73, 1318.35nm).

Picture1:12 wavelengths for LWDM

However, LAN WDM typically uses four or eight channels. If using four channels, the transmit data can reach 100g. If using eight channels, the transmit rate can reach 400G.

Main Features of LWDM

1. Short-Distance Optimization

LWDM is designed for local networks, like data centers and campus networks. Unlike long-haul DWDM, it operates effectively over distances generally less than 40 km.

2. Sutible Channel Spacing

LAN WDM has the advantages of CWDM’s cost-effectiveness and DWDM’s wide range. It uses narrower spacing than CWDM but wider than DWDM, typically 4.26 nm to 4.62nm for 4 to 8 wavelengths. So it has a balance between cost and capacity.

3. Specific Wavelength Bands

LAN WDM operates within the O-band (1260-1360 nm). Therefore, it is compatible with standard single-mode fiber (SMF) for short distances to ensure low dispersion and cost efficiency.

4. High-Speed Support

LWDM aggregates multiple channels (e.g., 4×25 Gbps = 100 Gbps) to support 25, 40, and 100 Gigabit Ethernet and beyond in LAN environments. LWDM technology realizes 100G-400G transmission capability through 4/8 channel aggregation, and supports multiple transmission standards (such as 100GBASE-LR4/ER4) and modulation technologies (NRZ/PAM4).

5. Fiber Efficiency

It maximizes the existing fiber infrastructure by multiplexing multiple signals, which is critical in densely packed data centers or enterprise cabling.

6. Simplified Deployment

Unlike long-haul DWDM systems, there is no requirement for complex amplification or dispersion compensation.

Application of LWDM

LWDM is primarily specified for use in transceivers, as it is mainly based on 25 Gbps per lane.

For example, the QSFP-100G-LR4 is a 100G QSFP28 LR4 transceiver designed for single-mode fiber (SMF) over a distance of 10 km. It features a transmitter with a cooled 4×25 Gb/s LAN WDM EML TOSA operating at wavelengths of 1295.56, 1300.05, 1304.58, and 1309.14 nm, and a receiver with 4×25 Gb/s PIN ROSA. This application utilizes 4 LAN WDM wavelengths within a single 4x25G QSFP28 LR4 optical module.

Conclusion

As network demands continue to rise, LWDM technology has significantly improved our network data rate and lowered our costs. We will use more related products in data centers and enterprise networks.

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