Abstract: An optical demultiplexer that separates, for each signal wavelength, signal light a plurality of wavelengths of which is multiplexed, the optical demultiplexer including: an antireflection film disposed at on an incident surface of a glass block; filters disposed on an emission surface of the glass block, the filters transmit light of a wavelength predetermined for each signal wavelength included in the signal light and reflect light of a wavelength other than the transmitting wavelength toward the incident surface; and a reflection film disposed on the incident surface of the glass block, wherein processing to reduce reflection of the reflection light into the glass block is applied on an optical path of the reflection light reflected by the filter disposed at an end away from the antireflection film.

Abstract: An optical demultiplexer that separates, for each signal wavelength, signal light a plurality of wavelengths of which is multiplexed, the optical demultiplexer including: an antireflection film disposed at on an incident surface of a glass block; filters disposed on an emission surface of the glass block, the filters transmit light of a wavelength predetermined for each signal wavelength included in the signal light and reflect light of a wavelength other than the transmitting wavelength toward the incident surface; and a reflection film disposed on the incident surface of the glass block, wherein processing to reduce reflection of the reflection light into the glass block is applied on an optical path of the reflection light reflected by the filter disposed at an end away from the antireflection film.

Abstract: The present invention provides a method of improving soft ground.In this method, slurry formed by a mixture of cement-based hardener and water is supplied to the soft ground under pressure and is mixed with soft soil thereby to harden the same. Then, at least when a ground improvement machine having mixing propellers is penetrated into the above-mentioned soft soil, the cement-based hardening slurry is discharged from the mixing propellers.Further, in another method of improving soft ground according to the present invention, slurry formed by a mixture of cement-based hardener and water is supplied to the soft ground under pressure and is mixed with soft soil. Then, when deep and short walls, both consisting of mixed layer of the cement-based hardening slurry and the soft soil are formed one after the other, a plurality of deep walls are formed at a distance therebetween and then the short walls are jointly formed between a plurality of these deep walls.