Fibre Link

The FL-IFU Subsystem consists of two main components: the Fiber Link (FL) sub-unit and the IFU sub-unit. The FL sub-unit is responsible for collecting and redistributing light using fused-silica fibers, defining the interfaces with other instrument work-packages, such as the front-ends, calibration unit, and spectrometers. It also designs the paths, modules, and elements required to transfer light between these subsystems. Meanwhile, the IFU sub-unit focuses on designing the IFU front-end, which reimages the ELT focal plane at different spatial scales and feeds the fiber bundle necessary for the IFU observing mode. Both components are developed to meet the top-level requirements that define the two baseline observing modes: seeing-limited mode and IFU mode.

In seeing-limited mode, ANDES operates with all spectrographs in parallel, collecting spectra across the full wavelength range. The front-end module reimages and splits the ELT light into spectral bands, each of which is injected into a large fiber. In the fiber-to-fiber module (F2FM), the light passes through a double-scrambler, homogenising the field, and a pupil splicer, which redistributes it into a bundle of smaller fibers. These fibers are arranged linearly to form the spectrometer slit, with two identical modules feeding the upper and lower sections of the slit.

In IFU mode, wavelengths shorter than 950 nm are used for SCAO correction, while spectra from 950–1800 nm are collected using the YJH spectrometer. The IFU module reimages the ELT focal plane through an optical zoom, injecting the light into a 2D array of microlenses. These microlenses transfer the light to a fiber bundle connected to the F2FM, which delivers it to a linear slit dedicated to the IFU spectrometer. Observations can be either on-axis (aligned with the SCAO reference target) or off-axis (within a 3” radius).