System and method for testing optical receivers

Abstract

Disclosed are a testing unit, system, and method for testing and predicting failure of optical receivers. The testing unit and system are configured to apply different values of current, voltage, heat stress, and illumination load on the optical receivers during testing. The test methods are designed to check dark current, photo current, forward voltage, and drift over time of these parameters.

1 . A testing unit for use in a system for testing and predicting failure of optical receivers, the testing unit comprising:
 a) a testing board configured to support at least one socket, wherein the at least one socket is configured to be coupled to a substrate configured to support at least one optical receiver; and   b) an emitter board configured to support at least one optical emitter;   wherein, the emitter board is supported adjacent to the testing board such that the emitter board is substantially parallel to the testing board and each of the one or more optical emitters on the emitter board is substantially aligned with a corresponding socket of the testing board.   
     
     
         2 . The testing unit of  claim 1  comprising at least one support rail configured to support and to attach the emitter board onto the testing board. 
     
     
         3 . The testing unit of  claim 1  comprising an edge connector on the emitter board, the edge connector configured to allow electrical communication between components on the emitter board and other components of the system. 
     
     
         4 . The testing unit of  claim 1  comprising a first connector located on the emitter board configured to allow electrical communication between the at least one optical emitter and the first connector. 
     
     
         5 . The testing unit of  claim 1  comprising a second connector configured to mate with the first connector located on the emitter board and to electrically connect the at least one optical emitter on the emitter board to the testing board. 
     
     
         6 . The testing unit of  claim 1  comprising electrical traces on the testing board configured to allow electrical communication between edge connector and the optical receivers on the substrates in the sockets on the testing board and to allow electrical communication between the emitters on the emitter board and the edge connector via the second connector. 
     
     
         7 . The testing unit of  claim 1 , wherein the optical receivers are photodiodes. 
     
     
         8 . The testing unit of  claim 1 , wherein the one or more optical emitters on the emitter board are configured to provide an illumination load on the at least one optical receiver on the testing board. 
     
     
         9 . The testing unit of  claim 1 , wherein the at least one socket is arranged on a top surface of the testing board. 
     
     
         10 . The testing unit of  claim 1 , wherein the at least one optical emitter is arranged on a bottom surface of the emitter board 
     
     
         11 . The testing unit of  claim 1 , wherein the electrical traces on the testing board are configured to allow electrical signals related to one or more testing methods to be sent from the edge connector to each of the optical receivers on the testing board and allow various parameters or outputs to be transmitted as electrical signals from each of the optical receivers to the edge connector. 
     
     
         12 . The testing unit of  claim 11 , wherein the parameters or outputs of the optical receivers are at least one of: an output voltage, an output current, and an operating temperature. 
     
     
         13 . The testing unit of  claim 1 , wherein the optical emitters are one of: vertical-cavity surface-emitting lasers (VCSELs), light emitting diodes (LEDs), and arrays of LEDs. 
     
     
         14 . The testing unit of  claim 1 , wherein when in an operational configuration, in which the bottom surface of the emitter board is substantially aligned with the testing board, the emitter board supports the same number of optical emitters as the number of sockets supported by the corresponding testing board and the configuration or orientation of these optical emitters matches that of the orientation of sockets of the testing board so as allow for optical communication between each optical emitter and the optical receivers in the socket beneath it. 
     
     
         15 . A system for testing and predicting failure of optical receivers, the system comprising:
 a) at least one testing unit according to  claim 1 ;   b) at least one driver in electrical communication with a plurality of optical receivers in one or more sockets on the testing board of the at least one testing unit and in electrical communication with the one or more optical emitters on the emitter board of the at least one testing unit via the end connector and electrical traces on the testing board; the driver configured to apply a voltage input to at least one optical receiver, to activate at least one optical emitter that is in optical communication with the at least one optical receiver, and to monitor a corresponding output parameter from the at least one optical receiver;   c) at least one control unit configured to execute or otherwise control the operation of the testing methods and procedures applied to the optoelectronic components supported by the testing unit via the at least one driver;   d) at least one power supply configured to supply electrical power to the at least one driver and to the control unit; and   e) electrical connections configured to allow electrical communication between the components of the system.   
     
     
         16 . A system according to  claim 15  additionally comprising at least one backplane element configured to support and be in electrical communication with the at least one testing unit; wherein, any number of testing units are supported by a backplane element and/or the system includes any number of additional backplane elements. 
     
     
         17 . A system according to  claim 15 , wherein the system does not include a backplane element and the testing unit is directly connected to a driver or to a control unit. 
     
     
         18 . A system according to  claim 15 , wherein the drivers include circuitry and/or optoelectronic elements configured to multiplex outputs signals received by the driver from testing units into a combined signal for transmission over a shared transmission medium to a control unit or other device in electrical communication with the driver. 
     
     
         19 . A system according to  claim 15 , wherein the at least one driver is further configured to determine a pass state or a fail state of any number of a plurality of optical receivers based on a comparison of various output parameters to corresponding output parameter thresholds. 
     
     
         20 . A system according to  claim 15 , wherein the control unit is in electrical communication with at least one sensor to monitor or control input, output, and/or ambient conditions of the system, wherein the at least one sensor is selected from the following: thermometers, pressure sensors, humidity sensors, accelerometers, photo resistors, and barometers. 
     
     
         21 . A system according to  claim 15 , wherein the control unit operates as a computer or computer program product. 
     
     
         22 . A system according to  claim 15 , wherein the processor includes or is associated with an apparatus comprising:
 a) a memory device configured to store various testing procedures, testing parameters, and/or threshold values configured to evaluate the reliability of a photodiode;   b) a processor configured to execute instructions stored in the memory device or otherwise accessible to the processor;   c) a communication interface configured as a device or circuitry embodied in either hardware or a combination of hardware and software that is configured to receive and/or transmit data either using wired or wireless techniques between at least one of: computing devices, servers, drivers, and testing units; and   d) a user interface in communication with the processor and configured to receive an indication of a user input and/or to provide an audible, visual, mechanical, or other output to a user.   
     
     
         23 . A system according to  claim 15 , wherein the driver includes some or all of the circuitry or operation of the control unit. 
     
     
         24 . A system according to  claim 21 , wherein the driver includes some or all of the circuitry or operation of the control unit. 
     
     
         25 . A system according to  claim 15  comprising sixteen optical receivers in eight sockets on sixteen testing boards, wherein the system is configured to be controlled by a single control unit; thereby enabling testing, with and without illumination, up to 2048 optical receivers without taking the optical receivers out of the system. 
     
     
         26 . A method of testing and predicting failure of optical receivers, the method comprising:
 A. placing the following components of a system for testing and predicting failure of optical receivers within a temperature controlled oven:
 a) a testing board configured to support at least one socket, wherein each socket is configured to receive a substrate configured to support at least one optical receiver; and 
 b) an emitter board configured to support at least one optical emitter; 
 wherein, the emitter board is supported above the testing board such that the emitter board is substantially parallel to the testing board and each of the one or more optical emitters on the emitter board is substantially aligned with a corresponding socket of the testing board; and 
   B. carrying out all tests without removing the testing board or the emitter board from the oven.   
     
     
         27 . The method of  claim 26 , wherein the optical receivers are photodiodes. 
     
     
         28 . The method of  claim 26 , wherein the method is carried out using a system that can be manually controlled or programmed to automatically carry out the reliability tests on individual optical receivers in any socket on any testing board. 
     
     
         29 . The method of  claim 26 , comprising a pre-test comprised of the following steps:
 a) check substrate temperature to determine if it is inside a designed operating range of an optical receiver;   b) check that an optical receiver to be tested is present;   c) apply current on the optical receiver and check that a measured voltage is inside a designed operating range of the optical receiver;   d) check for an open or a short circuit and leakage on the optical receiver;   e) in case of fail of any of steps a to d, the test stops.   
     
     
         30 . The method of  claim 26 , comprising a first test procedure comprised of the following steps:
 a) apply reverse voltage on the optical receiver and check that the dark current is inside the designed operating range of the optical receiver;   b) apply reverse voltage on the optical receive, turn on illumination, and check that the photo current is inside the designed operating range of the optical receiver;   c) apply forward current on the optical receiver and check that the forward voltage is inside the designed operating range of optical receiver;   d) in case of fail of any of the steps a to c, the optical receiver is marked as FAIL; and   e) in case no failure in steps a to c, document the dark current, photo current, forward voltage, and temperature at Time=0;   wherein in steps a and b the reverse voltage can be applied using different voltage values and in step c the forward current can be applied using different current values.   
     
     
         31 . The method of  claim 26 , comprising a second test procedure, which comprises the following two options:
 A) first option is without illumination:
 a) raise the temperature of a substrate above ambient; 
 b) apply a constant reverse voltage on an optical receiver. 
 c) measure the substrate temperature periodically and check if the temperature is above or below a preset value; and 
 d) if the temperature is above or below a preset value the test stops; 
 e) measure dark current periodically and check if inside a designed operating range of the optical receiver; and 
 f) in case of fail of step d the optical receiver is marked as FAIL. 
 wherein the test is carried out at a constant temperature. 
   B) second option with illumination:
 a) raise the temperature of a substrate; 
 b) apply a constant reverse voltage on an optical receiver and turn on illumination; 
 c) measure substrate temperature periodically and check if the temperature is above or below a preset value; 
 d) in case of fail the test stops; 
 e) measure photo current periodically and check if inside the designed operating range of the optical receiver; and 
 f) in case of fail of step e the optical receiver is marked as FAIL. 
   
     
     
         32 . The method of  claim 26 , comprising a third test procedure comprised of the following steps:
 a) apply reverse voltage on an optical receiver and check that the dark current is inside the designed operating range of the optical receiver;   b) apply reverse voltage on optical receiver, turn on illumination, and check that the photo current is inside a designed operating range of the optical receiver;   c) apply forward current on the optical receiver and check that the forward voltage is inside the designed operating range of the optical receiver;   d) in case of fail of any of the steps a to c, the optical receiver is marked as FAIL;   e) in case no failure in steps a to c, document the dark current, photo current, forward voltage, and temperature at Time=X.   f) determine drift of dark current, photo current, and forward voltage between Time=0 and Time=X and check if inside a designed limit for the optical receiver; and   g) in case the drift of one or more of the parameters is outside the designed limit the optical receiver is marked as FAIL;   wherein:
 i) in steps a and b the reverse voltage can be applied using different voltage values and in step c the forward current can be applied using different current values; and 
 ii) when computing the drift in step d the temperature and illumination conditions should be same at time=0 and time=X. 
   
     
     
         33 . The method of  claim 26 , wherein the first test procedure, the second test procedure, and the third test procedure are run consecutively and the data in the database from the first procedure is used for Time=0 in step f of the third procedure. 
     
     
         34 . The method of  claim 26 , wherein the second test procedure and the third test procedure are repeated cyclically and any measurement can be used as Time=0 allowing drift to be determined in step f of the third procedure.