Laser-based microalignment for fabrication of highly precise 2D fiber collimator arrays

Abstract

In optical communication there are systems requiring a parallel transmission of several high bit rate data channels based on single mode fibers. Especially for a free space transmission within such a system a precise collimation of the parallel channels is necessary to guarantee a low loss system. For this purpose compact two dimensional fiber collimator arrays can be used. A main quality characteristic for these arrays is the pointing accuracy, the angular deviation of the collimated beams to a theoretical optical axis. The angular deviation is caused by a lateral offset of the fiber axes to the axes of the corresponding micro lens. To minimize this offset we developed and analyzed an actor geometry for a fiber array which allows a laser based micro alignment of the fibers to the micro lenses. An alignment accuracy within sub microns can be realized which guarantees a pointing accuracy below 0.01 degrees. In this paper we demonstrate some important results of the FEM based analyzes to show the influence of different laser parameters on the actor behavior. Experimental results confirm the results of the FE analyzes and demonstrate the applicability of laser based micro alignment of fibers for the assembly of highly precise two dimensional fiber collimator arrays.

High precision optical fiber alignment using tube laser bending

“…Stark et al [11] used laser forming to align multiple fibers with respect to a micro-lens array with a pitch of 2 mm. One actuator consists of three 'legs' in a 'Y' shape, where each leg can be shortened by laser forming.…”

Laser forming for sub-micron adjustment: with application to optical fiber assembly

“…Due to the limited deformation magnitude and repeatability per irradiation step, the alignment process is usually a multi-step process. .9: (a):An array of 'Y' shaped actuators for aligning optical fibers to a microlens array [31]. The smallest displacement achieved with this actuator was 0.2 µm.…”

“…Stark et al [31] used this method to align multiple fibers with respect to a microlens array with a pitch of 2 mm, see Fig 1.9a. One actuator consists of three 'legs' in a 'Y' shape, where each leg can be shortened by laser forming.…”

“…There are three types of direct thermal forming mechanisms, which are referred to as the Temperature Gradient Mechanism (TGM), the Upsetting Mechanism (UM) and the Buckling Mechanism (BM) [14,22,44]. The first two mechanisms are mostly applied for sub-micrometer resolution adjustments [18,20,30,31].…”

“…This mechanism has been exploited in actuators with multiple degrees of freedom [30,31] and is the main mechanism occurring in laser-bending of tubes [13,14,48]. Unfortunately, accurate prediction of the displacements of an actuator based on the UM is not trivial.…”