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Laser Safety

 Caution

USE OF CONTROLS OR ADJUSTMENTS OR PERFORMANCE OF PROCEDURES OTHER THAN THOSE SPECIFIED IN THIS GUIDE MIGHT RESULT IN HAZARDOUS RADIATION EXPOSURE.

Due to the potential safety hazard that is posed by high power outputs of optical modules, the BTI7800 supports automatic power shutdown (APSD) and automatic power reduction (APR) to shut off or reduce the output powers when a fiber is cut.

Table 1: Timing of APSD and APR Operations

Laser Safety Mechanism

Activation Time

Output Level After Activation

APR

< 2.0 seconds

< 20 dBm

APSD

< 2.0 seconds

< 20 dBm

Laser Safety: Automatic Power Shutdown

Automatic power shutdown (APSD) applies to fiber spans between optical equipment. When a fiber is cut, APSD causes both ends to automatically shut down its high power lasers, allowing maintenance personnel to repair or reconnect the fiber safely. Once the span fibers are repaired or reconnected, the lasers are automatically turned back on and traffic is automatically restored.

Warning

APSD is performed in software on the service module and is disabled whenever the service module undergoes a warm or cold reload. In a cold reload, the lasers are turned off and are in a safe state. In a warm reload, however, the lasers remain on while APSD is disabled.

Without being limited to the foregoing, a service module might undergo a warm reload in the following situations:

  • The user issues an operator command that warm reloads the service module.

  • The user issues an operator command that cold or warm reloads the Chassis Management Module (CMM) in a single CMM system.

  • The user performs a software upgrade of the chassis.

  • The user restores a configuration database to the chassis.

  • The user replaces the CMM in the chassis. See Chassis Management Module Replacement.

  • Any situation where a CMM fails in a single CMM system or where both CMMs fail in a dual CMM system. See Chassis Management Module Failure or Removal.

APSD on the 96-Channel Amplifier

The 96-Channel Amplifier is capable of emitting high output powers. To guard against accidental exposure to high-powered lasers, the 96-Channel Amplifier supports automatic power shutdown (APSD). APSD shuts down the high output lasers in both directions when a fiber cut is detected.

The output WDM signal on the line port is automatically shut down, or disabled from turn-up, if either of the following conditions occurs:

  • (Cond. 1) A Loss of Light fault is active against the input WDM and input OSC on the same line port. This triggers the port to undertake APSD measures. The line port turns off its output WDM signal and simultaneously sends a shutdown signal on the OSC to the far end.

  • (Cond. 2) A shutdown signal is received from the far end OSC. The far end OSC sends a shutdown signal when APSD is triggered at the far end. In response to the shutdown signal, the near end line port turns off its output WDM signal, and keeps it turned off for as long as the shutdown signal persists.

Single Fiber-Cut Example

Starting with span fibers connected, and with the WDM and OSC operationally in-service, the following sequence of events occurs after the receive fiber is cut on the line port:

  1. WDM and OSC Loss of Light Receive faults are raised on the near end line port. The near end therefore meets (Cond. 1).

  2. The near end turns off its WDM output and sends an APSD shutdown signal on the OSC to the far end.

  3. When the far end receives the shutdown signal, the far end meets (Cond. 2) and shuts down its WDM output.

  4. Both fibers are no longer illuminated by the WDM, and the safety hazard is avoided.

When the fiber cut is repaired, or when the disconnected fiber is reconnected, the recovery proceeds as follows:

  1. The OSC Loss of Light Receive fault on the near end line port is cleared. The near end no longer meets (Cond. 1).

  2. The near end turns on its WDM output and stops transmitting the APSD shutdown signal to the far end.

  3. Since the far end no longer receives the APSD shutdown signal, the far end no longer meets (Cond. 2) and reenables the WDM output.

  4. Both the near end and the far end restore traffic onto the span.

Laser Safety: Automatic Power Reduction

To guard against accidental exposure to high power lasers, some ports support automatic power reduction (APR). APR reduces the output of the laser when a fiber cut is detected.

Warning

APR is performed in software on the service module and is disabled whenever the service module undergoes a warm or cold reload. In a cold reload, the lasers are turned off and are in a safe state. In a warm reload, however, the lasers remain on while APR is disabled.

Without being limited to the foregoing, a service module might undergo a warm reload in the following situations:

  • The user issues an operator command that warm reloads the service module.

  • The user issues an operator command that cold or warm reloads the Chassis Management Module (CMM) in a single CMM system.

  • The user performs a software upgrade of the chassis.

  • The user restores a configuration database to the chassis.

  • The user replaces the CMM in the chassis. See Chassis Management Module Replacement.

  • Any situation where a CMM fails in a single CMM system or where both CMMs fail in a dual CMM system. See Chassis Management Module Failure or Removal.

APR on 96-Channel Amplifier Modules

The 96-Channel Amplifier client and DCM ports are capable of emitting high output powers. To guard against accidental exposure to high power lasers, these ports support APR, which reduces the output of the laser when a fiber cut is detected.

The 96-Channel Amplifier supports two APRs:

  • Mid-stage between the DCM Out and DCM In ports. APR is triggered when a Loss of Light Receive (loLightRx) fault is detected at the DCM IN port of the 96-Channel Amplifier module. Once APR is triggered, the output of the laser on the DCM Out port is automatically reduced to a safe level.

  • Client Out port. APR is triggered when the optical back reflection (OBR) exceeds the threshold, and the output power is larger than 5 dBm. When APR is triggered, the output of the laser on the Client Out port is automatically reduced to a safe level.

Safety Rating and Label

All BTI7800 Series products meet the FDA requirements for a class 1 laser product with a Class 1M hazard rating:

LASER RADIATION DO NOT VIEW DIRECTLY WITH OPTICAL INSTRUMENTS CLASS 1M LASER PRODUCT

A caution label is located on each BTI7800 Series laser circuit pack. Two different labels are used depending on the circuit pack.

Figure 1: Laser Safety Warning Label with Text
Laser Safety Warning Label with Text
Figure 2: Laser Safety Warning Label Without Text
Laser Safety Warning Label Without Text
Caution

Read and understand all caution labels before working with the equipment.

BTI7800 Series Laser Output Ports

The BTI7800 Class 1M laser output ports are located on the following modules.

Table 2: Laser Output Ports

Module

Product Code (PEC)

Optical Wavelength

Port

96-Channel Amplifier

BT8A78AMP1

1528.77 nm to 1566.72 nm

DCM out

Line Out

C1 Out

96-Channel Fixed Mux/Demux

BT8A78MD03

1528.578 nm to 1566.928 nm

C1-C96 Out

L1 Out

Wavelength Protection Switch

BT8A78WPS4

C-band: 1500 to 1570 nm

O-band: 1260 to 1350 nm

L-band: 1560 to 1620 nm

C1 Out A

L1 Out B

L1 Out A

C2 Out A

L2 Out B

L2 Out A

C3 Out A

L3 Out B

L3 Out A

C4 Out A

L4 Out B

L4 Out A