1. Optical Transceiver Optical Path Issues:
In security monitoring and control projects, most optical cables are usually installed by users themselves, typically using G652 single-mode fiber. Since the system coverage is generally not large, the optical link loss of standard equipment (up to 20KM) is usually sufficient. Therefore, the optical transceiver does not require excessive optical path loss. However, users often encounter problems such as no image, image jitter, or poor image quality. Most of these issues occur at the fiber pigtails, jumpers, or adapters at the ends of the optical path, rather than in the main trunk line. Common causes include: 1. Incorrect insertion of fiber optic connectors; 2. Contamination of the fiber optic connector core (ceramic sleeve). The solutions are: 1. Reinsert the connector or replace the fiber jumper; 2. Clean the connector with 99.9% anhydrous ethanol and reinsert it; 3. Use a multimeter to check the video cable of the camera and confirm if there is a video signal present.
2. Optical Data Interface:
To meet the requirements of security monitoring systems, equipment such as matrices, hard disk recorders, and decoders provide RS-485 data interfaces. This type of interface has advantages like long transmission distance, strong load capacity, and can support four-wire full-duplex communication. Any two devices on the line can communicate bidirectionally, while a four-wire RS-422 bus only allows communication between master and slave devices, not between slaves. However, one disadvantage is that it uses a three-state configuration, which may cause instability or even "dead" communication. If there is no communication (i.e., the system goes offline), check the following: 1. Confirm whether there is any control signal. Use a multimeter to check the RS-485 port output from the controller (matrix, recorder, etc.) for a 10V signal. 2. Check if the RS-485 interface of the optical transceiver is functioning properly. If the UA-B voltage is zero, it's considered abnormal, and the pan/tilt function may not work. This issue can be caused by either reversed A+ and B- connections or serious impedance mismatch.
3. Optical Switch:
The switch signal is a TTL-level pulse train used to control warning lights, alarms, relays, and other devices. The load capacity of the switch interface depends on the current it can handle, such as the EW series optical transceiver, which supports up to 1.5A. 1. The EW series optical switch interface supports normally open buttons, but when connected as shown in the diagram, both normally open and normally closed modes are supported. 2. Digital interfaces cannot be directly connected in parallel and must use a distribution circuit if necessary. 3. Some customers attempt to use the RS-485 bus to transmit switch signals. Based on our experience, this method is not ideal and often leads to issues after a few days of operation. It may be due to faults in the RS-485 converter.
4. Transient Interference Hazards and Countermeasures for Optical Transceivers:
1. Generation of Transient Interference: Transient interference is often caused by large inductive loads, such as motor switching, transformer activation, relay operations, and especially during lightning strikes, where static induction can affect the optical transceiver. 2. Hazards of Transient Interference: Due to its high frequency, short duration, and large amplitude (hundreds of kilovolts), transient interference can damage critical components of the RS-485 interface chip and main chip. This is particularly severe during summer thunderstorms, causing significant trouble for users, businesses, and manufacturers. 3. Countermeasures: Although manufacturers use various protection methods, such as bypassing (self-healing diodes), absorption (bidirectional suppression diodes), and isolation (optocouplers), they still cannot completely prevent damage caused by transient interference. Frequent damage to the RS-485 interface places a heavy burden on both users and manufacturers.
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