Coherent light generators – Particular temperature control
Reexamination Certificate
2001-01-05
2003-06-24
Davie, James (Department: 2828)
Coherent light generators
Particular temperature control
C062S003200, C062S003700
Reexamination Certificate
active
06584128
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to broadband communications, such as cable television systems, and more specifically to optical devices, such as fiber transmitters, within the cable television systems that utilize thermoelectric coolers.
BACKGROUND OF THE INVENTION
A communication system
100
, such as a two-way cable television system, is depicted in FIG.
1
. The communication system
100
includes headend equipment
105
for generating forward signals that are transmitted in the forward, or downstream, direction along a communication medium, such as a fiber optic cable
110
, to an optical node
115
that converts optical signals to radio frequency (RF) signals. The RF signals are further transmitted along another communication medium, such as coaxial cable
120
, and are amplified, as necessary, by one or more distribution amplifiers
125
positioned along the communication medium. Taps
130
included in the cable television system split off portions of the forward signals for provision to subscriber equipment
135
, such as set top terminals, computers, and televisions. In a two-way system, the subscriber equipment
135
can also generate reverse signals that are transmitted upstream, amplified by any distribution amplifiers
125
, converted to optical signals, and provided to the headend equipment
105
.
Operators are continuing to revolutionize the conventional network architecture as depicted in
FIG. 1
, and more recently, have begun to consolidate headends within the network and extend longer fiber optic cable runs as shown in
FIG. 2. A
network deploying more fiber optic cable than conventional coaxial cable allows a centralized super headend
205
to be shared with sites that may be hundreds of miles away, thereby eliminating several headends
105
throughout the conventional network
100
. Emanating from the consolidated headend
205
in all directions are hubs
210
that serve several different sites within the network
200
. Fiber equipment enclosed in the hubs
210
distribute the optical signals generated from the headend
205
further through the network
200
until conversion of the optical signals to electrical signals by an optical node
215
. The electrical signals are then amplified by an amplifier
220
and continue downstream for the final transmission to the subscriber.
The fiber equipment included in the hubs
210
is generally optical transmitters and receivers, which are contained in racks. Generally, the fiber equipment consumes much of the hub space; therefore, internal airflow is closely monitored to ensure that the fiber equipment does not overheat. In addition to experiencing the heat generated by the fiber equipment, the hubs may become extremely hot in the summer months and extremely cold in the winter months, even though the hubs are traditionally enclosed and somewhat environmentally controlled. As a result, there are external fans for dissipating the heat away from the fiber equipment and cooling devices, such as thermoelectric coolers, designed within the fiber equipment that are used to electrically cool.
By way of example, a thermoelectric cooler (TEC) is used in the optical transmitter to assist in cooling and heating the laser within the transmitter. It is known that controlling the laser temperature to within the standard temperature rating of the laser significantly enhances signal quality of the optical transmission lasers. A laser may be physically attached to the top of the TEC and the whole package may then be hermetically sealed and placed on a heatsink, such as a metal chassis. Functionally, the TEC utilizes current flow to either cool or heat the laser package depending on the environment surrounding the laser. To cool the laser, which is generally the case, current will flow in one direction through the TEC. To heat the laser in the cases of extreme cold, the current will flow in the opposite direction. The amount of cooling or heating is controlled by the magnitude of the current flowing through the TEC.
Conventionally, switching techniques, linear regulation, or a bridge topology can be employed to control the magnitude and direction of current flow through the TEC. Additional details of the conventional regulation of current flow through the TEC are set forth, for example, in a design note by Unitrode DN-76, the teachings of which are incorporated herein by reference.
One conventional example of a device that controls the current through a TEC is depicted in FIG.
3
and further discussed in the Unitrode DN-76 publication, which describes the use of a bridge topology. More specifically, a thermistor
305
is used to detect any temperature fluctuations, and the resulting change in voltage is provided to a pulse width modulated (PWM) controller
310
, which is powered by a power supply
315
. A bridge topology
320
, that includes four field effect transistors (FETs) (not shown), and an LC filter
325
process the signal from the PWM controller
310
to regulate the direction and magnitude of current flow into the TEC
330
. Depending upon the magnitude and direction of the current flow, the TEC
330
will either heat or cool the control surface
335
. A heatsink
340
, such as a metal chassis, absorbs the heat from the surrounding components and the heat generated from the TEC
330
and transfers it away from the control surface
335
. An external fan
345
dissipates the transferred heat into the surroundings.
Utilizing the conventional methods, such as a bridge topology
320
, of regulating the TEC
330
consumes significant power. More specifically, the device to be cooled consumes power, and this power consumption in turn heats the surrounding area. As a result, additional cooling is often necessary. Thus, what is required is a method of regulating the current flow through a TEC
330
to maximize the power efficiency of the overall device in which it is included, and in addition, to minimize the heat generation that will adversely affect the surrounding components.
REFERENCES:
patent: 5936987 (1999-08-01), Oshihi et al.
patent: 6205790 (2001-03-01), Denkin et al.
patent: 6519949 (2003-02-01), Wernlund et al.
Unitrode Application Note, UC1637/2637/3637 Switched Mode Controller for DC Motor Drive, Unitrode Corporation, 7 Continental Blvd., Merrimack, NH, 03054.*
Salerno, David, Unitrode Design Note, Closed Loop Temperature Regulation Using the UC3638 H-Bridge Motor Controller and a Thermoelectric Cooler, Unitrode Corporation, 7 Continental Blvd., Merrimack, NH, 03054.
Barnhardt III Hubert J.
Couturier Shelley L.
Davie James
Massaroni Kenneth M.
Scientific-Atlanta, Inc.
LandOfFree
Thermoelectric cooler driver utilizing unipolar pulse width... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Thermoelectric cooler driver utilizing unipolar pulse width..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thermoelectric cooler driver utilizing unipolar pulse width... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3159442