1. An optical amplifier for amplifying an optical signal, the amplifier comprising:
an optical amplification section including an amplification medium doped with an active substance for optical amplification and an excitation light source which emits excitation light that is provided to the amplification medium so that optical amplification occurs in the amplification medium; and
a constant-gain control section finding out target excitation light power to be set according to a change in the level of an input optical signal on the basis of a correlation between a gain and excitation light power to obtain a target gain, finding out a target drive signal for making the excitation light source emit the target excitation light power on the basis of a correlation function between a drive signal for driving the excitation light source and excitation light power, and exercising constant-gain control over the optical amplification section by a feedforward control system,
wherein the constant-gain control section generates the correlation function according to a change in characteristics of the excitation light source which changes due to degradation over time, between a drive signal and excitation light power by varying the drive signal and by regularly measuring excitation light power, and finds out a target drive signal from the target excitation light power on the basis of the correlation function.
2. The optical amplifier according to claim 1, wherein
the input optical signal includes a plurality a different wavelengths that are wavelength division multiplexed together, and
the constant-gain control section has a correlation between gain and excitation light power for different numbers of wavelengths being included in the input optical signal, and,
to obtain the target gain, the constant-gain control section finds out, from the correlation between gain and excitation light power, target excitation light power corresponding to a change in the level of the input optical signal caused by a change in the number of wavelengths actually included in the input optical signal.
3. The optical amplifier according to claim 1, further comprising a degradation alarm giving section for recognizing a degree of degradation of the excitation light source from a correlation slope of the correlation function and for performing alarm giving control.
4. A gain control method comprising:
recognizing a level of an input optical signal input to an optical amplification medium that is provided with excitation light to cause the input optical signal to be optically amplified as the input optical signal travels through the optical amplification medium, the excitation light being provided by an excitation light source in accordance with drive signals for driving the excitation light source;
obtaining target excitation light power for realizing a target gain on the basis of the recognized level;
generating a correlation function according to a change in characteristics of the excitation light source which changes due to degradation over time, between a drive signal and excitation light cower by varying the drive signal and by regularly measuring excitation light power;
finding out a target drive signal corresponding to the target excitation light power on the basis of the generated correlation function; and
exercising constant-gain control with a feedforward control system by driving the excitation light source by the target drive signal.
5. The gain control method according to claim 4, further comprising:
recognizing a degree of degradation of the excitation light source from a correlation slope of the correlation function and performing alarm giving control.
6. A gain control apparatus comprising:
means for recognizing a level of an input optical signal input to an optical amplification medium that is provided with excitation light to cause the input optical signal to be optically amplified as the input optical signal travels through the optical amplification medium, the excitation light being provided by an excitation light source in accordance with drive signals for driving the excitation light source;
means for obtaining target excitation light power for realizing a target gain on the basis of the recognized level;
means for generating a correlation function according to a change in characteristics of the excitation light source which changes due to degradation over time, between a drive signal and excitation light power by varying the drive signal and by regularly measuring excitation light power;
means for finding out a target drive signal corresponding to the target excitation light power on the basis of the generated correlation function; and
means for exercising constant-gain control with a feedforward control system by driving the excitation light source by the target drive signal.
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 hybrid method of erecting a cold box in the field utilizing prefabricated and field erected components, said method comprising the following steps:
a. anchoring at least one column to a foundation in a substantially vertical orientation;
b. anchoring a pipe rack module to said foundation in a substantially vertical orientation, wherein said pipe rack module is in close proximity to said at least one column;
c. attaching interconnecting piping between said pipe rack module and said at least one column;
d. anchoring at least four corner beams to the edge of said foundation in a substantially vertical orientation;
e. attaching prefabricated panels with bracing to said corner beams, to form an enclosure around said column and piping; and
f. attaching a roof to said enclose.
2. The method of claim 1, wherein said pipe rack module is prefabricated.
3. The method of claim 1, wherein said pipe rack module comprises one or more elements selected from the group consisting of control valves, manual valves, sample connections, piping, pre-cut panels with valve actuators, instrumentation, vapo flash, lighting, ladders and platforms, pre-wired junction box, instrumentelectrical cable trays, piping support, duct to exchanger box, and the pump module.
4. The method of claim 1, wherein said at least one column comprises one or more elements selected from the group consisting of waste line, separator pots, large safety valve lines.
5. The method of claim 1, further comprising a second pipe rack module.
6. The method of claim 5, wherein said second pipe rack module comprises one or more elements selected from the group consisting of waste line, separator pots, large safety valve lines.
7. The method of claim 1, wherein said prefabricated panels are attached to said corner beams by bolting.
8. The method of claim 1, wherein said prefabricated panels are connected vertically or horizontally.
9. The method of claim 8, wherein said prefabricated panels are attached to the edge of said foundation or to adjacent prefabricated panels with bolts.