1. A digital demodulating apparatus comprising:
a plurality of circuit elements constituting a receiving unit and a demodulating unit that demodulates a signal received by the receiving unit;
a supplying unit that supplies power to each circuit element;
a correcting unit that corrects errors due to noises generated on a transmission path of the received signal;
a calculating unit that calculates a value indicating the quantity of noises contained in the signal when the correcting unit corrects the errors;
a judging unit that judges whether or not reception conditions of the received signal are good in a predetermined time period, on the basis of values repeatedly calculated by the calculating unit in the predetermined time period after a value calculated by the calculating unit indicates that the noises have become not more than a predetermined reference quantity; and
a reducing unit that reduces the power to be supplied to each circuit element by the supplying unit, when the judging unit decides that the reception conditions are good.
2. The apparatus according to claim 1, wherein the received signal is in the form of a signal train in which a plurality of unit signals each having a predetermined length are successively arranged,
the correcting unit corrects with respect to each unit signal the errors due to the noises generated on the transmission path of the signal train,
the calculating unit calculates a mean value of values indicating the respective quantities of noises with respect to a plurality of unit signals, on the basis of the quantities of corrections performed by the correcting unit with respect to the plurality of unit signals, and
the judging unit judges whether or not the reception conditions of the received signal are good in the predetermined time period, on the basis of mean values repeatedly calculated by the calculating unit in the predetermined time period after a mean value calculated by the calculating unit indicates that the noises have become not more than the predetermined reference quantity.
3. The apparatus according to claim 2, wherein the judging unit decides that the reception conditions of the received signal are good in the predetermined time period, when any of the mean values repeatedly calculated by the calculating unit in the predetermined time period indicates that the noises have become not more than the predetermined reference quantity.
4. The apparatus according to claim 1, wherein the judging unit judges whether or not the reception conditions are good, on the basis of a relation between the variance of the whole of the values repeatedly calculated by the calculating unit in the predetermined time period, and a value indicating that the noises have become not more than the predetermined reference quantity.
5. The apparatus according to claim 1, wherein the correcting unit comprises a wave equalizing unit that applies wave equalization to each unit signal contained in a train of the received signal, and
the calculating unit calculates a modulation error ratio (MER) with respect to the wave equalization applied by the wave equalizing unit, as the value indicating the quantity of noises.
6. A controlling method of a digital demodulating apparatus comprising a plurality of circuit elements constituting a receiving unit and a demodulating unit that demodulates a signal received by the receiving unit; and a supplying unit that supplies power to each circuit element, the method comprising:
a correcting step of correcting errors due to noises generated on a transmission path of the received signal;
a calculating step of calculating a value indicating the quantity of noises contained in the signal when the errors are corrected in the correcting step;
a judging step of judging whether or not reception conditions of the received signal are good in a predetermined time period, on the basis of values repeatedly calculated in the calculating step in the predetermined time period after a value calculated in the calculating step indicates that the noises have become not more than a predetermined reference quantity; and
a reducing step of reducing the power to be supplied to each circuit element by the supplying unit, when it is decided in the judging step that the reception conditions are good.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of generating electric power in a wellbore, comprising:
placing a light cell at a desired depth in the wellbore, said light cell generating electric energy upon receiving light energy; and
supplying light energy from a source thereof over an optical fiber that extends into the wellbore from an earth surface to the light cell for generating the electrical energy downhole.
2. The method of claim 1 further comprising charging an electric energy storage device in the wellbore with the electrical energy produced by the light cell.
3. The method of claim 2 further comprising providing an electrically-operated device in the wellbore and operating said device utilizing the electrical energy from the storage device.
4. The method of claim 3 wherein the electrically-operated device is selected from the group consisting of a (a) sliding sleeve, (b) choke, and (c) flow control device.
5. The method of claim 1, further comprising communicating optical signals over the optical fiber between the earth surface and a downhole device.
6. The method of claim 2, wherein charging the electric energy storage device comprises charging a battery.
7. The method of claim 6, wherein charging the battery comprises trickle charging the battery.
8. A system for use with a wellbore, comprising:
a light cell adapted to be placed in the wellbore, the light cell to generate electric energy in response to receiving light;
a light conduit to extend from an earth surface into the wellbore, the light conduit to carry light to the light cell; and
a device coupled to the light cell to receive the electric energy from the light cell.
9. The system of claim 8, further comprising a light source to provide light to the light cell over the light conduit.
10. The system of claim 9, wherein the light conduit comprises an optical fiber.
11. The system of claim 10, further comprising another device for placement in the wellbore, the another device to communicate optical signals over the optical fiber.
12. The system of claim 8, wherein the device comprises an electric energy storage device.
13. The system of claim 12, wherein the electric energy storage device comprises a battery.
14. The system of claim 12, further comprising another device electrically connected to the electric energy storage device.