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HFBR-5912E Datasheet(PDF) 5 Page - Agilent(Hewlett-Packard) |
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HFBR-5912E Datasheet(HTML) 5 Page - Agilent(Hewlett-Packard) |
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5 / 16 page  5 Eye Safety Circuit For an optical transmitter device to be eye-safe in the event of a single fault failure, the transmit- ter must either maintain eye-safe operation or be disabled. In the HFBR-5912E there are three key elements to the laser driver safety circuitry: a monitor diode, a window detector circuit, and direct control of the laser bias. The window detection circuit monitors the average optical power using the monitor diode. If a fault occurs such that the transmitter dc regulation circuit cannot maintain the preset bias conditions for the laser emitter within ± 20%, the transmitter will automatically be disabled. Once this has occurred, an electrical power reset or toggling the transmit disable will allow an attempted turn-on of the transmitter. If fault remains the transmitter will stay disabled. The HFCT-5912E utilizes an optical subassembly consisting of a short piece of single mode fiber along with a current limiting circuit to guarantee eye-safety. It is intrinsically eye safe and does not require shut down circuitry. Signal Detect The Signal Detect circuit provides a TTL low output signal when the optical link is broken or when the transmitter is OFF as defined by the Gigabit Ethernet specification IEEE 802.3z, Table 38.1. The Signal Detect threshold is set to transition from a high to low state between the minimum receiver input optional power and -30 dBm avg. input optical power indicating a definite optical fault (e.g. unplugged connector for the receiver or transmitter, broken fiber, or failed far-end transmitter or data source). A Signal Detect indicating a working link is functional when receiving encoded 8B/10B characters. The Signal Detect does not detect receiver data error or error-rate. Data errors can be determined by signal processing offered by upstream PHY ICs. Electromagnetic Interference (EMI) One of a circuit board designer’s foremost concerns is the control of electromagnetic emissions from electronic equipment. Success in controlling generated Electromagnetic Interference (EMI) enables the designer to pass a governmental agency’s EMI regulatory standard and more importantly, it reduces the possibility of interference to neighboring equipment. Agilent has designed the HFBR/HFCT- 5912E to provide excellent EMI performance. The EMI performance of a chassis is dependent on physical design and features which help improve EMI suppression. Agilent encourages using standard RF suppression practices and avoiding poorly EMI-sealed enclosures. Radiated Emissions for the HFBR-5912E and HFCT-5912E have been tested successfully in several environments. While this number is important for system designers in terms of emissions levels inside a system, Agilent recognizes that the performance of most interest to our customers is the emissions levels, which could be expected to radiate to the outside world from inside a typical system. In their application, SFF transceivers are intended for use inside an enclosed system, protruding through the specified panel opening at the specified protrusion depth. Along with the system advantage of high port density comes the increase in the number of apertures. Careful attention must be paid to the locations of high- speed clocks or gigabit circuitry with respect to these apertures. While experimental measurements and experiences do not indicate any specific transceiver emissions issues, Agilent recognizes that the transceiver aperture is often a weak link in system enclosure integrity and has designed the modules to minimize emissions and if necessary, contain the internal system emissions by shielding the aperture. To that end, Agilent’s gigabit MT-RJ transceivers (HFCT-5912E and HFBR-5912E) have nose shields which provide a convenient chassis connection to the nose of the transceiver. This nose shield improves system EMI performance by closing off the MT-RJ aperture. Localized shielding is also improved by tying the four metal housing package grounding tabs to signal ground on the PCB. Though not obvious by inspection, the nose shield and metal housing are electrically separated for customers who do not wish to directly tie chassis and signal grounds together. The recommended transceiver position, PCB layout and panel opening for both HFBR-5912E and HFCT-5912E are the same, making them mechanically drop- in compatible. Figure 6 shows the recommended positioning of the transceivers with respect to the PCB and faceplate. |
Similar Part No. - HFBR-5912E |
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Similar Description - HFBR-5912E |
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