Optically coupled device and optical module including optically coupled device

An optically coupled device to which a photoelectric conversion device on which a photoelectric conversion element that emits or receives light is formed and a multi-mode optical fiber can be attached, including an optical fiber positioning mechanism for positioning the optical fiber when the optical fiber is attached, and that can optically couple the photoelectric conversion element and an end surface of the optical fiber, the optically coupled device comprising:

• a first lens surface formed on a first surface of an optically coupled device main body facing the photoelectric conversion element when the photoelectric conversion device is attached, the first lens surface used to form an optical path connecting the photoelectric conversion element and the end surface of the optical fiber;
• an optically coupled device-side photoelectric conversion device positioning mechanism formed on the first surface and used to position the photoelectric conversion device when the photoelectric conversion device is attached;
• and
• a second lens surface formed on a second surface of the optically coupled device main body facing the end surface of the optical fiber when the optical fiber is attached, the second lens surfaces used to form the optical path connecting the photoelectric conversion element and the end surface of the optical fiber;
• wherein, an optical axis of the first lens surface is formed parallel to an emission or irradiation direction of light in the photoelectric conversion element when the photoelectric conversion device is attached;
• the optically coupled device is formed such that a device including a photoelectric conversion device-side photoelectric conversion device positioning mechanism that is engaged with the optically coupled device-side photoelectric conversion device positioning mechanism to position the photoelectric conversion device can be attached as the photoelectric conversion device;
• a following expression (1) can be satisfied
• 1.2≦β≦1.4 (1)
• where, β:NA1/NA2 (where, NA1 is a numeric aperture on a photoelectric conversion device-side of the optically coupled device main body and NA2 is a numeric aperture on an optical fiber-side of the optically coupled device main body);
• and
• with the photoelectric conversion device, a following expression (2) can be satisfied
• d1+d2+d3+d4+d5≦W (2)
• where, d1:
• a displacement amount of the photoelectric conversion device-side photoelectric conversion device positioning mechanism from an ideal formation position, and a displacement amount in a direction perpendicular to the emission or irradiation direction of light in the photoelectric conversion element
• d2:
• a deformation amount of the optically coupled device-side photoelectric conversion device positioning mechanism from an ideal form, and a deformation amount in a direction perpendicular to the optical axis of the first lens surface
• d3:
• a displacement amount of the first lens surface from an ideal formation position, and a displacement amount in the direction perpendicular to the optical axis of the first lens surface
• d4:
• a displacement amount of the photoelectric conversion element from an ideal formation position, and a displacement amount in the emission or irradiation direction of light in the photoelectric conversion element
• d5:
• a displacement amount of the optically coupled device-side photoelectric conversion device positioning mechanism from an ideal formation position, and a displacement amount in the direction perpendicular to the optical axis of the first lens surface
• W:
• an attachment position clearance width:
• a distance between an attachment position before movement and an attachment position after movement under an assumption that the photoelectric conversion device is moved along the direction perpendicular to the optical axis of the first lens surface, from an attachment position attaching to the optically coupled device main body at which optical coupling efficiency between the photoelectric conversion element and the end surface of the optical fiber is at a maximum efficiency set in advance, to an attachment position at which the optical coupling efficiency decreases by a degree equivalent to 1 dB in relation to the maximum efficiency.