Fiber optic combiner is a type of fiber optic connecting device that utilizes optical fiber precision fusion technology to maximize the coupling of optical power from the transmitting optical fiber to the receiving optical fiber while minimizing any impact on the system due to its presence in the optical fiber. path.
The fiber combiner plays a crucial role in fiber laser systems. Its quality not only directly affects the power and beam quality of the fiber laser, but also provides a crucial guarantee for the safe and stable operation of the laser.
Classification of fiber optic combiners
Based on their function, fiber combiners can be categorized into two types: power combiners and pump combiners.
- The bomb combiner combines multiple bomb beams into a single optical fiber for output. Its main objective is to increase the pump's power.
- The power combiner combines multiple single-mode lasers into a single optical fiber for output, with the aim of increasing the laser output power.
pump combiner
power combiner
Fiber combiners can also be classified based on their composition into two types: N×1 fiber combiners without signal fiber and (N+1)×1 fiber combiners with signal fiber.
The (N+1)×1 fiber combiner differs from the N×1 combiner in that it includes a signal fiber at its center. During the manufacturing process, N optical fibers must be arranged precisely and symmetrically around the signal fiber, which serves as the input for signal light.
Both the power combiner and the pump combiner fall into the N×1 combiner category. The specific function depends on the model of the N-channel input fibers.
If the N channel fibers are single-mode fibers or large-mode field fibers, they can be directly connected to N lasers to increase the laser output power, resulting in a power combiner.
If the N-channel fibers are multimode fibers, they are connected to N-pump sources to increase the laser pump power, forming a pump combiner.
N×1 Fiber Optic Combiner
(N+1) × 1 beam combiners are used specifically for pump beams and are primarily found in fiber optic amplification systems.
The central fiber in the combiner is a single-mode fiber that transmits signal light, while the surrounding N multimode fibers serve as pump fibers for pump light transmission.
This type of combiner is commonly used in MOPA (Master Oscillator Power Amplifier) configurations.
(N+1) × 1 fiber optic combiner
Side pump combiner and end pump combiner
The central fiber of the side pump combiner serves as the signal fiber, and its core is a single-mode or near-single-mode waveguide designed for laser transmission. The six peripheral fibers are used to transmit light from the pump.
Once these seven optical fibers are arranged in order, they are fused, stripped, and joined to the output double-jacketed optical fiber.
Ultimate Pumped Fiber Combiner
The main difference between a side-pump combiner and an end-pump combiner is that the pump fiber in a side-pump combiner is fixed to the signal fiber jacket without undergoing fusion or funneling, whereas in an end-pump combiner the signal the fiber is melted and tapered.
As a result, in principle, the signal transmission of a side pump combiner is superior to that of an end pump combiner.
Side Pumped Fiber Combiner
Beam combiner manufacturing
The power combiner has a basic structure composed of three parts: input fiber, fused conical fiber bundle and output fiber.
Basic structure of power combiner
To ensure that the fiber bundle merges and tapers well with the output fiber, the cross-section of the fiber bundle must be circular and the pump fibers must be arranged in a specific geometric pattern, typically in a regular hexagonal shape.
During the manufacturing process, the input fiber bundles are first assembled and then fused and tapered to form a fused tapered fiber bundle. The tapered waist of the fused tapered fiber bundle is then cut and fused with the output fiber.
A robust packaging and heat dissipation structure is designed to ensure the stability and longevity of the beam combiner. Copper or aluminum, with high thermal conductivity, are commonly used as the packaging shell, and a water cooling system can be integrated into the metal packaging as needed.
Fiber lasers connect fiber devices through welding. High-quality fiber fusion is crucial to achieving greater power. However, losses inevitably occur during the welding process, which accumulate light and heat over time, potentially leading to a deterioration in beam quality or damage to optical components.
