A flameproof optical fiber connection assembly for use in areas at risk of explosion, comprising: a first connector having a first optical fiber inlet and a first optical fiber outlet; a second connector having a second optical fiber inlet and a second optical fiber outlet; and a casting-compound free optical fiber connection unit interconnected between the first connector and the second connector and including a plurality of 4 to 12 optical fiber passages, each one of the optical fiber passages being configured to pass therethrough an optical fiber connected to the first optical fiber outlet and the second optical fiber inlet, each one of the plurality of optical fiber passages including an inner diameter sized to prevent flames or sparks from travelling through the passage and each one of the plurality of optical fiber passages being configured to allow a single optical fiber to pass therethrough; a plurality of tube members, each tube member including a single optical fiber passage formed as a through-hole within the tube member; and a tube receiving member having a plurality of through-bores, each through-bore being configured to receive one tube member, wherein each one of the plurality of through-bores is a stepped bore including a first bore section on a side facing the first connector and a second bore section on a side facing the second connector, wherein the first bore section includes an inner diameter larger than an outer diameter of the tube member and the second bore section includes an inner diameter smaller than the outer diameter of the tube member. a first connector having a first optical fiber inlet and a first optical fiber outlet; a second connector having a second optical fiber inlet and a second optical fiber outlet; and a casting-compound free optical fiber connection unit interconnected between the first connector and the second connector and including a plurality of 4 to 12 optical fiber passages, each one of the optical fiber passages being configured to pass therethrough an optical fiber connected to the first optical fiber outlet and the second optical fiber inlet, each one of the plurality of optical fiber passages including an inner diameter sized to prevent flames or sparks from travelling through the passage and each one of the plurality of optical fiber passages being configured to allow a single optical fiber to pass therethrough; a plurality of tube members, each tube member including a single optical fiber passage formed as a through-hole within the tube member; and a tube receiving member having a plurality of through-bores, each through-bore being configured to receive one tube member, wherein each one of the plurality of through-bores is a stepped bore including a first bore section on a side facing the first connector and a second bore section on a side facing the second connector, wherein the first bore section includes an inner diameter larger than an outer diameter of the tube member and the second bore section includes an inner diameter smaller than the outer diameter of the tube member. a plurality of 4 to 12 optical fiber passages, each one of the optical fiber passages being configured to pass therethrough an optical fiber connected to the first optical fiber outlet and the second optical fiber inlet, each one of the plurality of optical fiber passages including an inner diameter sized to prevent flames or sparks from travelling through the passage and each one of the plurality of optical fiber passages being configured to allow a single optical fiber to pass therethrough; a plurality of tube members, each tube member including a single optical fiber passage formed as a through-hole within the tube member; and a tube receiving member having a plurality of through-bores, each through-bore being configured to receive one tube member, wherein each one of the plurality of through-bores is a stepped bore including a first bore section on a side facing the first connector and a second bore section on a side facing the second connector, wherein the first bore section includes an inner diameter larger than an outer diameter of the tube member and the second bore section includes an inner diameter smaller than the outer diameter of the tube member.