Abstract:
An electronic fiberoptic power measuring instrument which utilizes a plurality of different detectors to ascertain the power of a light beam. The light beam that enters the instrument can be selectively altered to be directly transmitted to a primary detector or can be reflected to be transmitted to a secondary detector. The structure for altering the light beam takes the form of a movable member which is arranged to intersect the path of the light beam. The movable member can be moved to a plurality of different positions with a different meter function being obtained at each position.

Description:
BACKGROUND OF THE INVENTION 
     1) Field of the Invention 
     This invention relates to an instrument that is used to measure power and wavelength of a light beam within a fiberoptic cable. 
     2) Description of the Prior Art 
     Fiberoptics includes one or more optical fibers constructed of glass or plastic which are clad with material of lower refractive index. These optical fibers can be arranged in the form of a wire. The light loss, or attenuation, in optical fibers can be very low. The most common use at the present time of fiberoptics is in the field of communications. Light transmitted along an optical fiber is equivalent to an electrical signal being conducted along a wire. However, an optical fiber has a number of advantages over an electrical conducting wire. These advantages include a greater information carrying capacity as a single fiber can carry thousands of telephone conversations and also complete freedom from electrical interference. 
     When dealing with fiberoptic communications equipment, there is required maintenance and repair of fiberoptic cables. Fiberoptic technicians need certain maintenance and repair equipment with a common form of such equipment being an optical power meter. The power of the light within optical cables can vary between a −80 dBm (decibels) to a +30 dBm and beyond. Zero dBm equals 1 milliwatt (mw) of power. 
     In the past, an optical power meter could only measure the power within a certain power range and for a limited wavelength range. Therefore there is required two to three different optical power meters to effectively measure the power from −80 dBm to +30 dBm at all common wavelengths. It is also normally desirable to measure the wavelength of a light beam. Although wavelengths are capable of varying between 630 nm (nanometers) to 1700 nm, communication companies use selected wavelengths (650 nm, 850 nm, 1310 nm and 1550 nm) and with the advent of DWDM (Dense Wavelength Division Multiplexing) the wavelength band of between 1520 dBm and 1580 dBm. 
     It would be desirable to design a single optical power meter that could be utilized to measure both high power and low power of light levels within optical fibers and also could be utilized to measure the wavelength of the light within the commonly used band by communication companies. 
     SUMMARY OF THE INVENTION 
     An electronic fiberoptic power and wavelength measuring instrument comprising a housing which has an exterior surface upon which is mounted an optical port. This optical port is to be connected to a source of transmitted light with this light being collimated within the housing. The light is being transmitted directly to a primary detector. Mounted within the housing in close proximity to the primary detector and spaced therefrom is at least one secondary detector and possibly two secondary detectors. The beam of light is to be intersected by a movable member with the preferable form of the movable member being a pivotable wheel. The wheel can be pivoted and fixed in different locations with one location providing for direct transmission of the light beam to the primary detector and a second location being for reflection of a portion of the light beam to a secondary deflector. The movable member can also be moved so the light beam can be reflected to a further secondary reflector. Mounted on the wheel are different light filters that provide for the transmission and/or reflection of the light beam between the different detectors. 
     The primary objective of the present invention is to construct an electronic fiberoptic power and wavelength measuring instrument that eliminates the need for utilizing of different optical power measuring instruments and also eliminates the need for a separate wavelength measuring instrument. 
     Another objective of the present invention is to construct an electronic fiberoptic and power wavelength measuring instrument which is small in size and therefor is deemed to be readily portable and can be carried by a technician to be used at a job site. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exterior frontal view of the instrument of the present invention showing the display panel of the instrument and the keyboard; 
     FIG. 2 is a right side view of the instrument of FIG. 1; 
     FIG. 3 is back view of the instrument of FIG. 1; 
     FIG. 4 is a view showing the housing of the instrument being located in an open position with the housing being divided into a front half and a back half; 
     FIG. 5 is a cross-sectional view through a portion of the instrument taken along line  5 — 5  of FIG. 2 showing in more detail the movable member that is positioned to intersect the light beam that is to be beamed within the instrument with the position of the movable member permitting direct transmission of the light beam to the primary detector; 
     FIG. 6 is a cross-sectional view taken along line  6 — 6  of FIG. 5; 
     FIG. 7 is a cross-sectional view similar to FIG. 5 taken along line  7 — 7  of FIG. 2; 
     FIG. 8 is a cross-sectional view similar to that of FIG. 7 but showing the movable member in a different position; 
     FIG. 9 is a cross-sectional view similar to that of FIG. 8 but showing the movable member in a still further different position; 
     FIG. 10 is a cross-sectional view similar to that of FIG. 9 but showing the movable member in a still further different position; and 
     FIG. 11 is a block diagram of the electronic circuitry that is utilized in conjunction with the instrument of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring particularly to the drawings, there is shown in FIGS. 1-4 the electronic fiberoptic power measuring instrument  20  of this invention. The instrument  20  has a plastic housing  22  which is formed of a front half  24  and a rear half  26 . When the front half  24  is fixedly mounted to the rear half  26  by means of screw fasteners  28  there is formed an enclosed internal chamber  30 . Mounted within the internal chamber  30  of the front half  24  is an electronic circuit board  32 . A similar circuit board  34  is mounted within the rear half  26 . A signal cable interconnects the circuit boards  32  and  34 . Also connected from the circuit boards  32  and  34  is a power cable  40 . Mounted on each of the circuit boards  32  and  34  are a mass of electrical and electronic components that are necessary for the operation of the instrument  20  of this invention. Power to the instrument  20  is supplied by a series of batteries that are mounted within the battery compartment which is covered by a battery compartment cover  42 . The batteries may be recharged by a recharger (not shown) that connects with recharging connector  74 . 
     Electronic readings of the instrument  22  are to be displayed within a display screen  44  formed within the front half  24 . The front half  24  also includes a keyboard  46  which includes an on/off button  48 . Indicator light  50  informs the user that the instrument  20  is “on”. The keyboard  46  also includes a button  52  to cause the numerical power indicia to be displayed in mw (milliwatts) on the display screen  44 . Button  54 , if pushed, would cause the numerical indicia within the display screen  44  to be displayed in dBm (decibels). Activation of the button  56  for a period of one second will result in a relative difference to be displayed from an immediately previous numerical value. Button  58 , when activated, will result in the wavelength being displayed within the display screen. The power level will vary according to wavelength of the light being measured. Therefore, before making any power measurement, the user should press button  60  which will immediately display a selection of calibration wavelengths to be selected from. This instrument will be preprogrammed and calibrated with normal wavelengths of 850 nm, 980 nm, 1300 nm, 1310 nm, 1550 nm and 1625 nm. The last used wavelength will be initially displayed at power up (for example 850 nm). If this is the approximate wavelength of the light, then the user should then proceed to make the power measurement. However, if the approximate wavelength value is other than the selected one, then the button  60  is to be pressed again which will display the wavelength value of 980 nm. Repeated pressing of button  60  will result in the further preprogrammed and calibrated values being displayed. When the correct approximate wavelength value is displayed, the power measurement is then to be taken. 
     In order to store any displayed value, it is only necessary to push the store button  62 . To recall that numerical value at a later time, it is only necessary to push the recall button  64 . The up and down buttons  66  and  68 , respectively, are to be pushed in order to scroll through different numerical values prior to recalling of a desired value. Pushing of button  70  will turn on and off the backlight for the display screen  44 . The backlight of the display screen  44  works through backlight lead  70  mounted on the circuit board  32 . Instrument  20  of this invention could be connected to a separate printer, which is not shown, by utilizing of connector  72 . Printing of the displayed material on the display screen  44  is to be accomplished by pushing of the print button  76 . Pushing of the button  78  will cause the instrument to display on the display screen  74  the different options that are available using of the instrument  20  such as automatic shut-off and to what decimal place the numerical values are to be displayed. 
     Mounted on the circuit board  34  is an electrical motor  38 . Mounted on the circuit board  32  are a pair of micro-controllers  80  and  82 . Also mounted on the circuit board  32  are display controllers  84  and  86 . The display controllers  84  and  86  work in conjunction with the display screen  44 . 
     Motor  38  causes rotation of a shaft  88  which is mounted within a motor shaft mount  90 . The motor shaft  88  is formed into a worm gear  92 . The worm gear  92  is to be in continuous contact with a ring gear segment  94 . The ring gear segment  94  is mounted on a wheel  96 . The wheel  96  is pivotally mounted on a pin  98  which is fixedly mounted on the rear half  26  of the housing  22 . The wheel  96  is mounted within chamber  100  which is formed within a block  102  which is fixedly mounted by rivets  104  to the rear half  26  of the housing  22 . The wheel  96  includes a hollow center  106 . Located within the hollow center  106  is a U-shaped block  108 . The U-shaped block  108  is to be mounted on the inside surface of a cover plate  110 . The cover plate  110  is designed to be fixedly secured by screw fasteners  112  to the block  102  completely enclosing of chamber  100 . However, light in the form of a light beam that is contained within optical fiber cable  114  is to be transmitted in the direction of arrow  116  into optical port connector  118 . The optical port connector  118  is fixedly mounted by appropriate screw fasteners, which are not shown, to the block  102 . The optical port connector  118  extends exteriorly of the plastic housing  22 . 
     Typically, the one end of the optical cable  114  is connected to the adapter  120 . This adapter  120  connects to the optical port  118 . It is desirable to have this light beam be narrowed within the instrument  20  and included within the optical port connector  118  is a collimator, which is not shown, which collimates the light into a parallel beam of approximately 1 mm in diameter. This 1 mm in diameter light beam is transmitted through passage  122  formed within the block  102 . The passage  122  connects with the chamber  100 . 
     The U-shaped block  108  includes a hollowed-out section  124 . The pin  98  is mounted within plastic tube  126  which is formed as part of the wheel  96 . A washer assembly  128  mounts the upper end of the pin  98  to the tube  126 . The wheel  96  is restrained against movement toward and away from the block  102  but is permitted to move relative to the block  102 . A plate  130  is mounted on the U-shaped block  108 . Mounted on the plate  130  is a photo detector defined as the primary detector  132 . Photo detectors are well known in the field of fiberoptics and need not to be described here in any particular detail and are relatively purchasable on the open market. The primary detector  132  connects through a cable assembly  134  to a plug  136  with this plug  136  being mounted to the printed circuit board  34 . Normally, the primary detector  132  will be constructed of Indium Gallium Arsenide (InGaAs). This primary detector  132  is to be sensitive to light within the wavelength range of 850 nm to 1700 nm. 
     Mounted on U-shaped block  108  are a pair of small light sources  138  and  140  usually light emitting diodes (LEDs). Separating the light sources  138  and  140  is a separating wall  142 . The light sources  138  and  140  are aligned in a direction parallel to the longitudinal center axis of the pin  98 . The light sources  138  and  140  are to be electrically activated with both the light sources  138  and  140  being on all the time the instrument  20  is on. When the instrument  20  is initially activated, the worm gear  92  is turned so that the wheel  96  will be pivoted to an “at home” position which is detected by the light from light source  140  passing through hole  144  formed within the wheel  96  and this light being detected by light detector  146  which is mounted on plate  148 . The plate  148  is fixedly mounted by bolts  158  to the block  102 . The light from the light source  140  after passing through the hole  144  passes through a hole  160  formed within the block  102  prior to being beamed onto light detector  146 . Upon the light detector  146  sensing light through the hole  144 , the worm gear  92  is deactivated and the “at home” position of the wheel  96  is established. When in the “at home” position, the beam of light from cable  114  is conducted through passage  122  and through hole  150  of the wheel  96  and in contact with the primary detector  132 . The power of that light beam if it is between −80 dBm to +5 dBm will be detected and displayed digitally on the display screen  44  as long as the user has pressed button  54 . If the user wishes to display the power in watts, the button  52  is to be pressed. 
     If the user determines that the wavelength of the light beam passing through passage  122  is not within the power range of −80 dBm to +5 dBm, the user can then press button  58  once which will cause the motor  38  to be activated turning of worm gear  92  and pivoting of the wheel  96  a prescribed number of degrees until hole  152  aligns between the light source  140  and the light detector  146  at which time the motor  38  will be deactivated and the wheel  96  will then be stopped which will position hole  154  in position to intersect the light beam passing through the passage  122 . The hole  154  is covered by a filter  156 . For the purpose of this invention, a filter is defined as a small glass chip that can either transmit light, reflect light or accomplish varying degrees of both. In this particular instance, the filter  156  will transmit light at a decreased power level which is precisely 25 dB less. The primary detector  132  is only accurate up to about +5 dBm. However, since the filter  156  decreases the intensity of the light by 25 dB, that means that the primary detector  132  is now accurate up to +30 dBm. Therefore, with the light beam passing through the filter  156 , the primary detector  132  can be used to accurately detect power up to +30 dBm and the software within the electronic circuitry of the instrument  20  of this invention will automatically register that the light beam is passing through the filter  156  and change the digital readings being displayed on the display screen  44  accordingly. 
     Simultaneously to when the light source  140  is beamed to the light detector  146 , light source  138  beams light through a hole  162  formed within the wheel  96  and hole  164  formed within the block  102  to then be picked up by light detector  166 . The light detector  166 , as well as light detector  146 , are mounted on the plate  148 . When the wheel  96  is moved from the “at home” position, the wheel  96  continues to move until the hole  152 , which has been previously mentioned, aligns with the light source  138  and is picked up by light detector  166  at which time the wheel  96  is then stopped. 
     Upon the user then hitting button  58  a second time, the wheel  96  is then caused to pivot again by activation of the motor  38 . The movement of the wheel  96  is to continue until hole  168  aligns with the light source  138  and is picked up by light detector  166  which then shuts down the motor  38 . At this particular position, the light beam passing through the passage  122  comes into contact with filter  170 . The filter  170  is to both transmit light and reflect light. The reflected light is to be transmitted through passage  172  to secondary detector  174 . The secondary detector  174  will normally be of the same type of detector as the primary detector  132 . It is to be noted that at a certain minimum wavelength (1530 nm), eighty percent of the light will be reflected with twenty percent of the light being transmitted. At a maximum value wavelength (1580 nm), it is also known that about eighty percent will be transmitted and twenty percent will be reflected. The software contained within the instrument  20  will ascertain what percentage of the wavelength is being transmitted to the primary detector  132  and what percentage is being reflected to the secondary detector  174 . These percentage values of transmitted light and reflected light will be compared to preprogrammed values within the software and from that determine the actual wavelength of the light beam that is being transmitted through the passage  122 . This wavelength value is displayed on the display screen  44  when button  60  is pressed. The instrument  20  of this invention can only be used at this time to calculate light wavelength within the range of 1520 nm to 1580 nm. However, this range of wavelength is in exceedingly common usage in communication so this wavelength calculation is a significant feature. 
     Upon the wavelength button  60  being again pressed along with button  64 , the wheel  96  will then begin pivoting clockwise until hole  176  aligns with the light source  138  and light is detected by light detector  166 . At that time, the motor  38  is again to be shut down and the filter  178  will be aligned with the passage  122 . The filter  178  comprises one hundred percent mirror with all the light being reflected through passage  180  to silicon detector  182 . The detector  182  is capable of measuring the power of the wavelength of light from 450 nm to 1000 nm. 
     The detector  174  is connected by cable assembly  184  to the printed circuit board  34  by means of plug  186 . The detector  182  is connected by a cable assembly  188  which is also to be connected to the circuit board  34  by means of plug  189 , in FIG. 4 of the drawings. The light detectors  146  and  166  transmit signals through cable assembly  190  to plug  192  to the circuit board  34 . 
     During the time that the instrument  20  of this invention is not being operated, protective cap  194  is to be placed about the optical port connector  118  covering such to protect the optical port connector  118  from contamination. The protective cap  194  is permanently attached by a strap  210  to the rear half  26  of the housing  22 . The rear half  26  of the housing  22  includes a pivotally movable stand brace  196  which is basically of a U-shaped configuration and is intended to be pulled outward by the user so that the instrument  20  can be placed in a semi-upright position when in use. 
     Referring particularly to FIG. 11 of the drawings, the primary detector  132  is electrically connected through an amplifier  198  to an analog digital convertor  200 . The amplifier  198  is to operatively driven by the microcontroller  80  within a preset range by means of a potentiometer  202 . Both the amplifier  198  and the convertor  200  are to be supplied a source of electrical power of +5V. Also, the convertor  200  is to receive a −5V of power. 
     The secondary detector  174  similarly operates through an amplifier  204  and a analog digital convertor  206  to the microcontroller  80 . Again, the amplifier  203  and the convertor  206  are to receive a +5V of electrical power with the convertor  205  also receiving a −5V of power. 
     The motor  38  is to be operatively driven by a motor control  208  which is mounted on the circuit board  34  and is connected to the microcontroller  80 . The position sensor module which includes plate  148  is also connected to the microcontroller  80 . It is the job of the position sensor module to determine the position of the wheel  96 . The keyboard  46  supplies input into the microcontroller  80 . The microcontroller  80  supplies an output to an LCD display  208  which digitally displays the values on the display screen  44 .