The Verizon technician was absolutely right - fiber links can indeed be too short for certain transceivers. When dealing with multi-mode fiber (MMF) connections between devices in the same rack or adjacent racks, the received optical power can exceed the receiver's maximum input power specification.

From your diagnostics, we see:

Juniper TX: -5.06 dBm → CoreSwitch RX: -5.87 dBm (GE)
CoreSwitch TX: ? → Juniper RX: -5.25 dBm (GE)
10G Link 1 RX: -8.92 dBm (comfortable range)
10G Link 2 RX: -3.04 dBm (potentially problematic)

Typical SFP/SFP+ specifications for 1G/10G MMF:

• Maximum receiver power: Usually around 0 dBm to -1 dBm
• Minimum receiver power: Typically -17 dBm to -20 dBm
• Optimal operating range: -10 dBm to -3 dBm (varies by vendor)

Your 10G link showing -3.04 dBm is particularly concerning as it's approaching the upper safety limit.

General rules for adding optical attenuators:

if (receivedPower > maxReceiverSensitivity - 3dB) {
    // Consider adding attenuation
    requiredAttenuation = receivedPower - (maxReceiverSensitivity - 3dB);
}

Practical example calculation for your 10G link:

// Assuming max receiver power is -1 dBm
float maxRxPower = -1.0; 
float currentRxPower = -3.04;
float safetyMargin = 3.0; // Recommended 3dB buffer

float requiredAttenuation = currentRxPower - (maxRxPower - safetyMargin);
// -3.04 - (-1 - 3) = -3.04 - (-4) = 0.96 dB
// Round up to next standard attenuator: 1dB or 3dB

Here's how to programmatically check power levels on common platforms:

Juniper JunOS (Python Example)

from jnpr.junos import Device
from jnpr.junos.op.diag import OpticsDiag

dev = Device(host='switch1', user='admin', password='xxxx')
dev.open()

optics = OpticsDiag(dev).get()
for intf, data in optics.items():
    print(f"{intf}: TX {data['laser-output-power']} dBm, RX {data['laser-rx-power']} dBm")

dev.close()

Cisco/Dell OS10 (Ansible Example)

- name: Gather optical diagnostics
  dellos10_command:
    commands: 
      - "show interfaces {{ item }} transceiver details"
    provider: "{{ cli }}"
  loop: "{{ interfaces }}" 
  register: optical_data

- name: Parse optical power
  set_fact:
    optical_power: |
      {% for item in optical_data.results %}
      {{ item.item }}: {{ item.stdout[0] | regex_search('Rx Power.*\\n') }}
      {% endfor %}

Common attenuator types for LC MMF:

1. Always check transceiver specifications for minimum/maximum power levels
2. Measure actual received power before installing attenuators
3. Start with lower attenuation values (3dB first) and verify
4. Consider using fixed attenuators for permanent links
5. Document all attenuation values in network documentation

Instead of attenuators, you could:

• Use higher loss patch cables (OM1 instead of OM3/4)
• Add extra fiber loops (careful not to exceed bend radius)
• Configure optical power reduction in SFP+ if supported

When dealing with fiber optic connections between co-located equipment (like switches in the same rack), many network engineers overlook a critical factor: minimum required attenuation. The Verizon technician was absolutely correct - excessive optical power can indeed damage receivers when cable runs are too short.

// Sample SFP+ power threshold check (Python-style pseudocode)
def validate_rx_power(current_dbm, sfp_type):
    thresholds = {
        '1000BASE-SX': {'min': -9.5, 'max': 0},
        '10GBASE-SR': {'min': -11.1, 'max': -1}
    }
    if not thresholds[sfp_type]['min'] <= current_dbm <= thresholds[sfp_type]['max']:
        raise OpticalPowerError(f"Power level {current_dbm}dBm out of range for {sfp_type}")

Your Juniper's -5.06dBm TX and -5.25dBm RX values are actually borderline for 1000BASE-SX (OM2). The 10GBASE-SR (OM3) reading of -3.0356dBm on port te0/6 is particularly concerning - it's approaching the upper safety limit.

For your specific scenario:

• Juniper GE link: 5dB attenuator would bring RX to -10.25dBm (ideal)
• 10G link on te0/6: 5-7dB attenuator recommended
• Other 10G links: 3dB sufficient

# Cisco IOS command to verify after attenuation
show interfaces transceiver details | include Optical|dBm

Always maintain RX power between -9dBm to -3dBm for 1G, and -11dBm to -1dBm for 10G. When in doubt:

1. Check manufacturer's datasheet for exact thresholds
2. Use variable attenuators for fine-tuning
3. Monitor BER (Bit Error Rate) after adjustments

A financial datacenter we worked with lost three $3,500 QSFP28 ports before realizing their 2-meter OM4 patch cables were delivering +1.2dBm - well above the -1dBm maximum. The solution was implementing fixed 5dB attenuators in all intra-rack connections.