Production process flow of pigtail collimator

The production of a pigtail collimator involves fiber preparation, lens alignment, epoxy or fusion assembly, polishing, coating, and final testing to ensure diffraction-limited collimation.

1. Fiber Preparation

The process begins with selecting the appropriate single-mode or multi-mode fiber. One end of the fiber is cleaved and angle-polished to minimize back reflections, often at 6–8° for FC/APC connectors . The fiber may also be AR-coated at the design wavelength to reduce reflection losses .

2. Lens and Housing Preparation

The collimator uses an aspheric or GRIN lens fixed inside a metal or stainless steel housing . The housing may be angled or straight depending on the focal length and design requirements. The lens surfaces are often AR-coated to maximize transmission and minimize insertion loss.

3. Assembly

There are three main assembly types:

• Epoxy-joint collimators: The fiber is threaded through a ferrule and fixed with heat-curing epoxy, then aligned with the lens .
• Air-gap collimators: A small air gap is maintained between the fiber end and lens, with AR coatings on adjacent surfaces .
• Fused collimators: The fiber is fusion-spliced directly to an index-matched lens for minimal loss . During assembly, precise alignment is critical. The fiber and lens are adjusted to minimize angular deviation and off-axis displacement, as even 0.1° misalignment can cause significant coupling loss .

4. Polishing and Connectorization

After assembly, the fiber end and ferrule are polished, often at an angle, to ensure smooth optical surfaces . The other end of the fiber is terminated with a connector such as FC/PC, FC/APC, or SMA, depending on the application .

5. Coating and Sealing

The collimator housing is hermetically sealed to maintain stability over temperature variations and prevent contamination . Coatings on the lens and fiber end reduce reflection and improve optical performance.

6. Testing and Calibration

Each collimator undergoes optical testing to verify collimation quality, insertion loss, and return loss . Standard collimators may be used to calibrate production units, ensuring diffraction-limited performance at the design wavelength. Additional tests may include beam profile measurement and alignment verification.

7. Customization

The fiber type, length, connector type, and wavelength can be customized for specific applications, including visible and near-IR spectral regions . Optional components, such as isolators or birefringent materials, can be inserted into the collimated beam during assembly. This workflow ensures that pigtail collimators achieve high optical performance, low insertion loss, and mechanical stability, suitable for OEM and laboratory applications.