Free-Space Compact CWDM 1x6 (+1) Multiplexer/Demultiplexer

The Free-space Compact CWDM 1x6 (+1) is a high-performance coarse wavelength division multiplexer designed for next‑generation fiber optic communication systems. Using a compact free‑space optical architecture rather than bulkier in-line filter assemblies, it combines or separates up to six CWDM channels plus one upgraded or common port in a single, space‑efficient module. This design enables system integrators and network engineers to dramatically increase fiber capacity and optimize network topology without the need for additional dark fiber.

Engineered around the ITU-T standardized CWDM frequency grid from 1271 nm to 1611 nm (or 1270 nm to 1610 nm, depending on configuration), this device delivers low insertion loss, excellent channel isolation, and superior long‑term stability. Typical insertion loss is as low as 1.3 dB, helping to preserve optical power budgets even in extended link distances or cascaded architectures. The 13–15 nm passband bandwidth around each channel wavelength ensures reliable operation with a wide range of CWDM transceivers and modulation formats, supporting current and future system upgrades.

The module is built with SMF‑28e compatible fiber in 900 μm loose tube, making it easy to integrate into existing single‑mode infrastructures. High return loss (≥ 45 dB) and directivity (≥ 55 dB) help to minimize back reflections and crosstalk, which is crucial for maintaining signal integrity in dense wavelength environments and bidirectional links. With polarization dependent loss (PDL) as low as 0.2 dB and polarization mode dispersion (PMD) typically 0.2 ps, the CWDM unit supports high‑speed data rates and is well suited for applications that demand stable, polarization‑insensitive performance.

A key distinction of this compact free-space CWDM versus many conventional filter‑based designs is its combination of small footprint and rugged optical alignment. The package size of 44 × 28 × 6 mm (excluding boots), with custom form factors available, allows for easy deployment in space‑constrained platforms such as transponder modules, compact data center equipment, edge routers, and mobile backhaul nodes. The robust free-space optics and mechanical design provide ultra‑stable operation over a wide range of environmental conditions, making the device suitable for both controlled indoor environments and more demanding field installations.

The 1x6 (+1) topology supports both unidirectional and bidirectional WDM configurations, which is particularly advantageous in networks where upstream and downstream traffic must share the same fiber pair. The additional “+1” port can be used as a common port, upgrade port, or express channel for future wavelength expansion or network reconfiguration. This flexibility simplifies network planning and offers a cost‑effective migration path as bandwidth requirements grow, without major re‑cabling or re‑engineering of the physical layer.

With adjacent channel isolation typically 35 dB and non‑adjacent isolation up to 45 dB, the module effectively suppresses interchannel interference, enabling higher spectral efficiency and cleaner signal separation at receivers. Com‑upgrade port isolation of up to 15 dB further assists in maintaining clear boundaries between existing and additional wavelengths, which is important when overlaying new services on top of legacy traffic. The device supports maximum optical input power up to 300 mW, leaving ample margin for high‑power transmitters, optical amplifiers, or extended reach configurations.

Designed for both commercial and industrial environments, the Free-space Compact CWDM 1x6 (+1) is available with operating temperature ranges from -5 to +70 °C for standard telecom and data center deployments, and from -40 to +85 °C for harsh outdoor or uncontrolled locations such as access networks, metropolitan rings, and remote terminals. Storage temperatures span -40 to +85 °C, safeguarding product integrity during shipping, warehousing, and system integration. These extended temperature capabilities, combined with the inherently stable free-space optical path, support long‑term reliability and reduced maintenance in demanding field conditions.

The module is ideally suited for optical add/drop multiplexing in CWDM backbone and metro rings, front‑haul and back‑haul in wireless networks, enterprise campus and data center interconnects, as well as other telecom and metro network architectures. It can be deployed in point‑to‑point links, ring topologies, or star and mesh configurations, allowing operators to consolidate multiple services—such as Ethernet, Fibre Channel, SONET/SDH, CPRI/eCPRI, and video—onto a single pair of fibers. By leveraging standardized CWDM wavelengths, it supports interoperability across a wide ecosystem of transceivers, amplifiers, and monitoring equipment.