1. An optical frequency locking method for tuning each of a plurality of narrow-band optical channel transmit signals to a respective dedicated optical channel frequency, the channel transmit signals having arbitrary channel frequency spacings, the method comprising, for each channel transmit signal, the steps of:
(a) tapping-off a portion of the optical power of the channel transmit signal to be tuned and filtering the tapped-off channel transmit signal using at least one optical filter device having a periodic transfer function, at least one of the channel frequency spacings of the channel transmit signals being unequal to the periodicity of the transfer function;
(b) monitoring, as an optical input signal, the optical power of the channel transmit signal supplied to the at least one optical filter device, and monitoring, as an optical output signal, the optical power of the filtered channel transmit signal; and
(c) tuning, within a predetermined locking range for the dedicated optical channel frequency, the optical frequency of the respective channel transmit signal such that a predetermined value for a target ratio is reached, the target ratio comprising the ratio of the optical output signal and the optical input signal corresponding to the respective dedicated optical channel frequency, wherein the predetermined locking range is defined by,
(i) determining a first spectral distance between the respective dedicated channel frequency and a first neighboring point at a lower frequency having the same value of the ratio of the optical output and input signal as the predetermined value of the target ratio and determining a second spectral distance between the respective dedicated channel frequency and a second neighboring point at a higher frequency having the same value of the ratio of the optical output and input signal as the predetermined value of the target ratio, and
(ii) using as the locking range either the whole range between the first and second neighboring points, or the range between the frequencies defined by the respective dedicated optical channel frequency plus and minus the smaller one of the first and second spectral distance.
2. The method of claim 1, wherein the predetermined value of the target ratio is either (i) calculated using the transfer function of the at least one optical filter device and the frequency spectrum of the transmit signal at the respective dedicated optical channel frequency, or (ii) measured, during a calibration process, using the at least one optical filter device and the channel transmit signal tuned to the respective dedicated optical channel frequency.
3. An optical frequency locking device for tuning each of a plurality of narrow-band optical channel transmit signals to a respective dedicated optical channel frequency, the channel transmit signals having arbitrary frequency spacings, the device comprising:
(a) at least two optical filter devices, each having a periodic transfer function, at least one of the channel frequency spacings of the channel transmit signals being unequal to the periodicity of the transfer functions and the transfer functions being different from each other;
(b) an optical splitter arrangement adapted to tap off a portion of the power of the channel transmit signal to be tuned and to split the tapped-off channel transmit signal into a first channel transmit signal and into at least two second channel transmit signals each of the at least two second channel transmit signals being supplied to a respective one of the at least two optical filter devices;
(c) a first detector means adapted to detect, as an input signal, absolute or relative values of the optical power of the first channel transmit signal, and at least two second detector means, each adapted to detect, as an output signal, absolute or relative values of the optical power of the second channel transmit signal filtered by a respective one of the at least two optical filter devices; and
(d) a controller device adapted to receive, from the first and second detector means, the detected values of the input and output signals, and to create, for an optical transmitter unit creating the channel transmit signal, a tuning signal such that the optical frequency of the channel transmit signal is tuned, within a predetermined locking range for the respective dedicated optical channel frequency, such that a predetermined value for a target ratio is reached, the target ratio comprising the ratio of the output signal and the input signal corresponding to the respective dedicated optical channel frequency, wherein the controller device selects, according to stored, calculated or received information for the respective dedicated optical channel frequency, which of the at least two optical filter devices and which of the input or output signals are to be used for tuning the optical transmitter unit, and wherein the controller device is adapted to create the tuning signal for the optical transmitter unit such that the optical frequency of the channel transmit signal is tuned to a value at which the predetermined value for the target ratio corresponding to the respective dedicated optical channel frequency is reached.
4. The optical frequency locking device of claim 3, wherein the controller device is adapted to control the tuning process such that, at the beginning of the tuning process, the optical frequency of the channel transmit signal is tuned to an initial value lying within the predetermined locking range for the respective dedicated optical channel frequency.
5. The optical frequency locking device of claim 3, wherein the predetermined value for the target ratio for each dedicated optical channel frequency and each of the at least two optical filter devices is stored within the controller device or wherein the controller device calculates these values based on stored information concerning the transfer function of the at least two optical filter devices.
6. The optical frequency locking device of claim 3, wherein the predetermined locking range for each dedicated channel frequency and each of the at least two optical filter devices is stored within the controller device or wherein the controller device calculates these values based on stored information concerning the transfer function of the at least two optical filter devices.
7. The optical frequency locking device of claim 3, wherein the controller device selects, according to stored, calculated or received information for the respective dedicated optical channel frequency, that instead of a selected one of the ratios of the output and input signals of the two optical filter devices, the ratio of a first and a second output signal is used for tuning the optical transmitter unit.
8. The optical frequency locking device of claim 3, wherein the periodic transfer functions of the at least two optical filter devices have essentially the same periodicity and are shifted versus each other by a predetermined frequency shift, the frequency shift lying within a range of 15 to 35 percent of the channel spacing.
9. The optical frequency locking device of claim 3, wherein the tapped-off channel transmit signal is included within a WDM transmit signal, wherein a means adapted to effect an amplitude modulation of the channel transmit signal to be tuned with a predetermined given modulation frequency and a given modulation depth is provided, and wherein the first and second detector devices are adapted to detect the channel transmit signal to be tuned and the filtered channel transmit signal in a phase-sensitive manner.
10. An optical frequency locking method for tuning each of a plurality of narrow-band optical channel transmit signals to a respective dedicated optical channel frequency, the channel transmit signals having arbitrary channel frequency spacings, the method comprising, for each channel transmit signal, the steps of:
(a) tapping-off a portion of the optical power of the channel transmit signal to be tuned;
(b) supplying the tapped-off portion of the optical power of the channel transmit signal to be tuned to each of at least two optical filter devices, the respective tapped-off channel transmit signal being filtered by the corresponding optical filter device, each of the at least two optical filter devices having a respective periodic transfer function, at least one of the channel frequency spacings of the channel transmit signals being unequal to the periodicity of each of the transfer functions and the transfer functions being different from each other;
(c) monitoring as a first optical output signal the optical power of the tapped-off channel transmit signal filtered by a first one of the optical filter devices and monitoring as a second optical output signal the optical power of the tapped-off channel transmit signal filtered by a second one of the optical filter devices; and
(d) tuning, within a predetermined locking range for the dedicated optical channel frequency, the optical frequency of the respective channel transmit signal such that a predetermined value for a target ratio is reached, the target ratio comprising the ratio of the first and second output signals corresponding to the respective dedicated optical channel frequency.
11. The method of claim 10, wherein the periodic transfer functions of the at least two optical filter devices have essentially the same periodicity and are shifted versus each other by a predetermined frequency shift.
12. The method of claim 11, wherein the predetermined locking range is defined by:
(a) determining a first spectral distance between the respective dedicated optical channel frequency and a first neighboring point at a lower frequency having the same value of the ratio of the first and second optical output signals as the predetermined value of the target ratio and determining a second spectral distance between the respective dedicated optical channel frequency and a second neighboring point at a higher frequency having the same value of the ratio of the first and second optical output signals as the predetermined value of the target ratio; and
(b) using as the locking range either:
(i) the whole range between the first and second neighboring points, or
(ii) the range between the frequencies defined by the respective dedicated optical channel frequency plus and minus the smaller one of the first and second spectral distance.
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. Vacuum pumping method for reducing pressure in an enclosure, at least one primary pump and one secondary pump connected in series in a flow path of pumped gases and driven in same rotation direction by a first electric motor and a second electric motor, respectively, controlled by an electronic control module for modifying speeds of the two electric motors independently, the secondary pump having an inlet side and an outlet side, the inlet side of the secondary pump operatively connected to the enclosure, and the primary pump having an inlet side operatively connected to the outlet side of the secondary pump, comprising:
at least one step, during reducing pressure in the enclosure, of progressively increasing the rotation speed of the secondary pump in accordance with a rotation speed variation law of the secondary pump; and
at the same time progressively reducing the rotation speed of the primary pump in accordance with a rotation speed variation law of the primary pump;
the progressively increasing of the rotation speed of the secondary pump being in accordance with a rotation speed variation law of the secondary pump that comprises a slowly rising first step followed by a fast rising second step followed by a moderately rising third step, and
the progressively reducing of the rotation speed of the primary pump being in accordance with a rotation speed variation law of the primary pump that comprises a high-speed first step followed by a fast falling second step followed by a slowly falling third step.
2. Method according to claim 1, wherein the second step of fast rising rotation speed of the secondary pump is simultaneous with the second step of fast falling rotation speed of the primary pump.
3. Method according to claim 1, wherein the rotation speed of the secondary pump increases from a minimum rotation speed to its nominal rotation speed and the rotation speed of the primary pump is initially its nominal rotation speed and at the end of the pressure reduction procedure reaches a reduced rotation speed.
4. Method according to claim 3, wherein the secondary pump is selected with a nominal throughput higher than the nominal throughput of the primary pump and the ratio of their initial rotation speeds is chosen to be close to the ratio of the respective nominal throughputs of the secondary pump and the primary pump.
5. Method according to claim 4, wherein the ratio of the respective throughputs of the primary and secondary pumps is from about 10 to about 15.
6. Method according to claim 1, wherein the rotation speed variation law of the primary pump comprises a high-rotation speed first step during which the rotation speed of the primary pump is temporarily increased above its nominal rotation speed.
7. Method according to claim 6, wherein the high-rotation speed first step of the primary pump comprises an initial period at a rotation speed close to the nominal rotation speed followed by an overspeed period at a rotation speed higher than the nominal speed.
8. Method according to claim 1, wherein the rotation speed variation laws of the primary pump and the secondary pump are chosen to reduce the overall power consumption.
9. Method according to claim 1, wherein the rotation speed variation laws of the pumps are generated as a function of pressure.
10. Method according to claim 1, wherein the rotation speed variation laws of the pumps are generated as a function of the elapsed time.
11. Vacuum pumping device for reducing pressure in an enclosure, comprising:
at least one primary pump and one secondary pump connected in series in a flow path of pumped gases and driven by a first electric motor and a second electric motor, respectively, the secondary pump having an inlet side and an outlet side, the inlet side of the secondary pump operatively connected to the enclosure, and the primary pump having an inlet side operatively connected to the outlet side of the secondary pump,
an electronic control module that controls the first electric motor and the second electric motor, and modifies speeds of the two electric motors,
the electronic control module comprising speed control means comprising a first controlled power supply unit adapted to supply power to the first motor, and a second controlled power supply unit adapted to supply power to the second motor,
a processor for controlling the first power supply unit and the second power supply unit to modify the speeds of the electric motors, characterized in that the processor has an associated memory containing a program for controlling the first power supply unit and the second power supply unit in accordance with the rotation speed variation laws of the pumps, and
at the end of the procedure for lowering the pressure in the enclosure, the speed control means reduce the rotation speed of the secondary pump from its nominal rotation speed or higher to its minimum rotation speed and kinetic energy of the secondary pump recovered in the form of electrical energy by controlling the second electric motor to brake the second pump, and the electrical energy reinjected via the electronic control module into the first electric motor for driving the primary pump.
12. Device according to claim 11, comprising at least one pressure sensor for sensing the pressure in the enclosure and producing a pressure signal that is sent to the processor, and wherein the program generates the rotation speed variation laws of the pumps as a function of the pressure signal.
13. Device according to claim 11, wherein the program generates the rotation speed variation laws of the pumps as a function of the elapsed time.
14. Vacuum pumping method for reducing pressure in an enclosure, at least one primary pump and one secondary pump connected in series in a flow path of pumped gases and driven in same rotation direction by a first electric motor and a second electric motor, respectively, controlled by an electronic control module for modifying speeds of the two electric motors independently, the secondary pump having an inlet side and an outlet side, the inlet side of the secondary pump operatively connected to the enclosure, and the primary pump having an inlet side operatively connected to the outlet side of the secondary pump, comprising the steps of:
progressively increasing, during reducing pressure in the enclosure, the rotation speed of the secondary pump in accordance with a rotation speed variation law of the secondary pump in which the rotational speed is increased in at least three steps; and
at the same time progressively reducing the rotation speed of the primary pump in accordance with a rotation speed variation law of the primary pump in which the rotational speed is reduced in at least three steps;
wherein the rotation speed of the secondary pump is progressively increased in accordance with a rotation speed variation law of the secondary pump that comprises a slowly rising first step followed by a fast rising second step followed by a moderately rising third step; and
wherein the rotation speed of the primary pump is progressively reduced in accordance with a rotation speed variation law of the primary pump that comprises a high-speed first step followed by a fast falling second step followed by a slowly falling third step.
15. Method according to claim 14, wherein the second step of fast rising rotation speed of the secondary pump is simultaneous with the second step of fast falling rotation speed of the primary pump.
16. Method according to claim 14,
wherein the rotation speed of the secondary pump increases from a minimum rotation speed to its nominal rotation speed and the rotation speed of the primary pump is initially its nominal rotation speed and at the end of the pressure reduction procedure reaches a reduced rotation speed, and
wherein the secondary pump is selected with a nominal throughput higher than the nominal throughput of the primary pump and the ratio of their initial rotation speeds is chosen to be close to the ratio of the respective nominal throughputs of the secondary pump and the primary pump.
17. Vacuum pumping method for reducing pressure in an enclosure, at least one primary pump and one secondary pump connected in series in a flow path of pumped gases and driven in same rotation direction by a first electric motor and a second electric motor, respectively, controlled by an electronic control module for modifying speeds of the two electric motors independently, the secondary pump having an inlet side and an outlet side, the inlet side of the secondary pump operatively connected to the enclosure, and the primary pump having an inlet side operatively connected to the outlet side of the secondary pump, comprising the steps of:
progressively increasing, during reducing pressure in the enclosure, the rotation speed of the secondary pump in accordance with a rotation speed variation law of the secondary pump in which the rotational speed is increased in at least three steps; and
at the same time progressively reducing the rotation speed of the primary pump in accordance with a rotation speed variation law of the primary pump in which the rotational speed is reduced in at least three steps;
wherein the rotation speed variation law of the primary pump comprises a high-rotation speed first step during which the rotation speed of the primary pump is temporarily increased above its nominal rotation speed, and
wherein the high-rotation speed first step of the primary pump comprises an initial period at a rotation speed close to the nominal rotation speed followed by an overspeed period at a rotation speed higher than the nominal speed.