A 1 meter silica multimode fiber of 600 microemeter core diamter was used to collect the side scattered light from side of hollow core fiber. The spectrum of scattered pump light was measured by an optical spectrum analyzer (YOKOGAWA AQ6370D) in the near-IR spectral region. In the side scattering measurement, the hollow core fiber was placed in groves of a aluminium plate and the multimode fiber tilted and approached to the hollow core fiber as close as possible to achieve the maximum collection efficiency. The groves was used for consistent measuremement conditions and avoid fiber damage and bend.