Photodiode module and method of making same
AssigneeSumitomo Electric Industries, Ltd.
InventorsYasushi Fujimura, Yoshiki Kuhara
Life of this patent
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Abstract
This invention provides an analog PD module useful for a large number of channels and a digital PD module useful for a large power signal input because of its reduced distortion. The PD chip is fixed at a spot deviating by L tan .alpha. from the lens center in the direction of a projection of a vector TS from the highest edge (T) to the lowest edge (S), where L is the distance between the lens center and the PD. The fiber should deviate in the contrary direction. The orientation enables a beam emanating from the fiber end to pass the center of the lens and reach the PD by spreading on a direct line.
Claims21
A method of producing a photodiode module comprising the steps of:
- calculating a slanting angle .alpha. of an emanating beam refracted at an end (Q) of an optical fiber being cut obliquely of an angle .theta. and having a lowest edge (S) and a highest edge (T);
- calculating a deviation X=L tan .alpha. where L is a predetermined distance between the center (H) of a lens and a photodiode chip;
- mounting the photodiode chip at a point deviating for X=L tan .alpha. from a center (P) of a package;
- fixing the lens with aberration at a point at which the center (H) of the lens is distanced by L from the photodiode chip and coincides with the center (P) of the package in a direction vertical to the package;
- maintaining the obliquely cut optical fiber in an orientation in which the lowest edge (S) of the oblique end (ST) is closest to the central axis passing the lens center (H) and being normal to the package;
- moving the fiber in a plane vertical to the central axis and in a direction parallel to the central axis for seeking a point which gives the photodiode the smallest distortion with a desired sensitivity;
- and
- fixing the fiber at the point.
A method of producing a photodiode module comprising the steps of calculating a slanting angle .alpha. of an emanating beam refracted at an end (Q) of an optical fiber being cut obliquely of an angle .theta. and having a lowest edge (S) and a highest edge (T);
- calculating a deviation X =L tan .alpha. where L is a predetermined distance between the center (H) of a lens and a photodiode chip;
- mounting the photodiode chip at a point deviating by an amount .beta. (including .beta.=0) from a center (P) of a package;
- fixing the lens with aberration at a point at which the center (H) of the lens is distanced by L from the photodiode chip and coincides with a point deviating for .beta.+X from the center (P) of the package in a direction vertical to the package;
- maintaining the obliquely cut optical fiber in an orientation in which the lowest edge (S) of the oblique end (ST) is closest to the central axis passing the lens center (H) and being normal to the package;
- moving the fiber in a plane vertical to the central axis and in a direction parallel to the central axis for seeking a point which gives the photodiode the smallest distortion with a desired sensitivity;
- and
- fixing the fiber at the point.
A photodiode module comprising;
- an optical fiber having an obliquely-cut end (ST) with a lowest edge (S) and a highest edge (T) for emitting beams;
- a lens with aberration for converging the beams emitted from the optical fiber;
- and
- a photodiode (PD) chip for converting the converged beams into electric signals;
- wherein a center (O) of the photodiode deviates for L tan .alpha., where L is a predetermined distance between the center of the lens and photodiode (PD) and .alpha. is an angle of an emanating beam refracted at an end of the optical fiber, from a lens axis passing the center (H) of the lens in the direction of a projection of a vector TS in a plane vertical to the lens axis and the fiber end is fixed at a point deviating in a reverse direction of the projection of the vector TS and giving the smallest distortion to the photodiode.
Dependencies are inferred from the claim text.