Instrument: Fiber Subsystems
MEGARA has two different modes that correspond to
the two fiber bundles available: the Large Compact Bundle IFU (LCB)
and the Multi-Object Spectrograph (MOS) mode.
The Folded Cassegrain subsystems are as follows: 
- A mechanical interface plate (attached to the Folded Cassegrain rotator) shall provide support to the Field Lens, the IFU and MOS.
- A Field lens corrects the lack of telecenticity of the GTC focal station. The opto-mechanical axes of all the fiber bundles will be parallel among them.
- The 2D refractive microlens arrays shall couple the light at the focal plane of the telescope, defining the FOV to be introduced in the fiber, adapting F# from f/17 to f/3 to minimize FRD and providing a telescope pupil image on the 100 μm fiber core. The refractive microlenses have been manufactured by AMUS using standard semiconductor technologies, which allows very accurate shaping of the lens profile and precise positioning of the lenslets in the array.
- The fibers, organized in bundles, transport the light coupled via the microlenses to the pseudo slit at the entrance of the spectrographs. The selected fibers are FBP 100/140/170 from Polymicro. These provide a wide broadband spectral response, a good FRD and have a numerical aperture of 0.2 ± 0.02. SEDI is in charge of fiber bundles manufacturing.
- The fibers are placed in front of each spectrograph at the pseudo-slit position, where the focal plane is smoothly curved with a ROC of 1075 mm and a size of 119 mm. Two different pseudo-slits are being manufactured for the two MEGARA modes: the LCB pseudo-slit (which shall contain the fibers from the LCB and 8 positioners, marked in orange in the figure, that shall be used for sky substraction) and the MOS pseudo-slit (which shall contain the fibers from the other 92 positioners).
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