Status link for multi-channel optical communication systems

Abstract

A robust and redundant status link is established by a first multi-channel optoelectronic device with a second multi-channel optoelectronic device in a multi-channel communication link. Transmitter bias currents are effectively modulated with a status link modulation signal representative of status data and subsequently modulated with primary data modulation signals. The resulting signals are transformed into optical signals and transmitted over the link as main communication links combined with a status link. At the second device, the optical signals are received and converted to electrical signals. The receipt of the optical signals creates multiple receiver bias currents, which may be monitored to detect the status link modulation signal. The second device may adjust various operating parameters in response to the information conveyed by the status link. For instance, devices can use status links to operate above nominal eye safety limits and/or to adjust transmit power to compensate for degradation effects.

1 . In a first multi-channel optoelectronic device, a method of establishing a redundant status link with a second multi-channel optoelectronic device, the method comprising:
 generating a status link modulation signal from status data, the status link modulation signal comprising a low frequency modulation current and representative of the status data;   effectively applying the status link modulation signal to at least two transmitter bias currents to generate at least two status-link modulated transmitter bias currents;   modulating each status-link modulated transmitter bias current with a different primary data modulation signal to obtain at least two resulting signals, wherein each primary data modulation signal comprises a high frequency modulation current and represents a different primary data electrical signal received by the optoelectronic device;   providing each resulting signal to a different optical transmitter for transformation into at least two optical signals; and   transmitting the at least two optical signals over a multi-channel communication link to the second multi-channel optoelectronic device.   
     
     
         2 . The method of  claim 1 , wherein the status data is indicative of one or more conditions affecting the performance of the multi-channel communication link. 
     
     
         3 . The method of  claim 2 , wherein one or more conditions affecting the performance of the multi-channel communication link includes one or more of:
 a non-functional channel;   potential exposure of one or more optical signals to view; and   insufficient optical signal intensity.   
     
     
         4 . The method of  claim 1 , further comprising, detecting a redundant status link established by the second multi-channel optoelectronic device on at least two of a plurality of receive channels of the first multi-channel optoelectronic device. 
     
     
         5 . The method of  claim 4 , wherein detecting the redundant status link established by the second multi-channel optoelectronic device includes:
 receiving at least two optical signals by at least two optical receivers, each optical signal including primary data and status data, the status data being low frequency modulated over the primary data;   converting each of the at least two optical signals to at least two electrical signals, wherein a receiver bias current of each optical receiver is altered by the status data; and   detecting the receiver bias currents to extract the status data.   
     
     
         6 . The method of  claim 1 , further comprising, effectively applying the status link modulation signal to three or more transmitter bias currents to provide additional status link redundancy. 
     
     
         7 . The method of  claim 1 , wherein effectively applying the status link modulation signal to at least two transmitter bias currents to generate at least two status-link modulated transmitter bias currents includes:
 modulating a common reference voltage signal with the status link modulation signal to create a status-link modulated reference voltage signal;   retrieving at least two digital transmitter bias current values from memory; and   providing each digital transmitter bias current value and the status-link modulated reference voltage signal to a different one of at least two digital to analog converters to generate the at least two status-link modulated transmitter bias currents.   
     
     
         8 . The method of  claim 1 , wherein effectively applying the status link modulation signal to at least two transmitter bias currents to generate at least two status-link modulated transmitter bias currents includes:
 retrieving at least two digital transmitter bias current values from memory;   modulating each of the at least two digital transmitter bias current values with the status link modulation signal to create at least two digital status-link modulated transmitter bias current values; and   providing each digital status-link modulated transmitter bias current value to a different one of at least two digital to analog converters, each of the digital to analog converters converting a different one of the digital status-link modulated transmitter bias current values into an analog status-link modulated transmitter bias current.   
     
     
         9 . A method of actively maintaining eye safety while permitting operation of a multi-channel optical communication link above nominal eye safety limits, the method comprising:
 in a first multi-channel optoelectronic device including a plurality of transmitters for emitting optical signals over a plurality of transmit channels to a second multi-channel optoelectronic device and a plurality of receivers for receiving optical signals over a plurality of receive channels from the second optoelectronic device, establishing a redundant status link with the second optoelectronic device over two or more of the transmit channels;   determining that the optical signals received from the second optoelectronic device over the receive channels are not potentially exposed to view; and   sending status data over the status link to the second optoelectronic device indicating it is safe for the second optoelectronic device to transmit optical signals to the first optoelectronic device over the receive channels at an aggregate optical transmit power that is greater than a predetermined eye safety limit.   
     
     
         10 . The method of  claim 9 , wherein the second optoelectronic device establishes a redundant status link with the first optoelectronic device over two or more of the receive channels, determines that the optical signals transmitted by the first optoelectronic deice over the transmit channels are not potentially exposed to view, and sends status data to the first optoelectronic device indicating it is safe for the first optoelectronic device to transmit optical signals over the transmit channels at an aggregate optical transmit power that is greater than a predetermined eye safety limit. 
     
     
         11 . The method of  claim 10 , further comprising, receiving status data from the second optoelectronic device indicating it is safe to transmit optical signals over the transmit channels at an aggregate optical transmit power that is greater than a predetermined eye safety limit, and, in response to receiving the status data, transitioning to or maintaining operation in a transmit power mode where the aggregate optical transmit power of the optical signals transmitted over the transmit channels is greater than the predetermined eye safety limit. 
     
     
         12 . The method of  claim 10 , further comprising, in response to not receiving status data from the second optoelectronic device indicating it is safe to transmit optical signals over the transmit channels at an aggregate optical power that is greater than the predetermined eye safety limit, maintaining operation in or transitioning to a transmit power mode where the aggregate optical transmit power of the optical signals transmitted over the transmit channels is less than or equal to the predetermined eye safety limit. 
     
     
         13 . The method of  claim 12 , wherein the transmit power mode where the aggregate optical transmit power of the optical signals transmitted over the transmit channels is less than or equal to the predetermined eye safety limit is achieved by reducing the transmitter bias currents supplied to the transmitters, reducing the duty cycle of the transmitter bias currents, or both, relative to the transmit power mode where the aggregate optical transmit power of the optical signals is greater than the predetermined eye safety limit. 
     
     
         14 . The method of  claim 9 , further comprising, determining that the optical signals received from the second optoelectronic device over the receive channels are potentially exposed to view; and in response, not sending status data over the status link to the second optoelectronic device indicating it is safe for the second optoelectronic device to transmit optical signals to the first optoelectronic device over the receive channels at an aggregate optical transmit power that is greater than the predetermined eye safety limit. 
     
     
         15 . The method of  claim 9 , wherein determining that the optical signals received from the second optoelectronic device over the receive channels are not potentially exposed to view includes monitoring receiver bias currents of the receivers. 
     
     
         16 . A method of monitoring and compensating for degradation effects affecting a multi-channel optical communication link, the method comprising:
 in a first device communicably coupled to a second device via a plurality of transmit channels and a plurality of receive channels, establishing a redundant status link with the second device over two or more of the transmit channels, wherein the first device optically communicates with the second device over the transmit and receive channels using a first plurality of optical transmitters and a first plurality of optical receivers and the second device optically communicates with the first device over the transmit and receive channels using a second plurality of optical receivers and a second plurality of optical transmitters;   monitoring the status of the receive channels; and   transmitting status data indicative of the status of the receive channels to the second device over the status link,   wherein the second device receives the status data and, in response, adjusts the transmit power of one or more of the second plurality of optical transmitters.   
     
     
         17 . The method of  claim 16 , wherein monitoring the status of the receive channels includes observing and recording data indicative of the status of the receive channels, the data indicative of the status of the receive channels including digital receiver bias current values for the first plurality of receivers. 
     
     
         18 . The method of  claim 16 , wherein the second device:
 establishes a status link with the first device over two or more of the receive channels;   monitors the status of the transmit channels by observing and recording data indicative of the status of the transmit channels, the data indicative of the status of the transmit channels including digital receiver bias current values for the second plurality of optical receivers; and   transmits the status data indicative of the status of the transmit channels to the first device over the status link established with the first device.   
     
     
         19 . The method of  claim 18 , further comprising, receiving the status data indicative of the status of the transmit channels and, in response, adjusting the transmit power of one or more of the first plurality of optical transmitters. 
     
     
         20 . The method of  claim 19 , wherein, if a digital receiver bias current value for one or more of the second plurality of optical receivers is:
 lower than a predetermined minimum level, adjusting the transmit power of one or more of the first plurality of optical transmitters includes increasing the transmit power of the one or more of the first plurality of optical transmitters which emit optical signals received by the one or more of the second plurality of optical receivers; and   higher than a predetermined maximum level, adjusting the transmit power of one or more of the first plurality of optical transmitters includes decreasing the transmit power of the one or more of the first plurality of optical transmitters which emit optical signals received by the one or more of the second plurality of optical receivers.