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1550nm Polarization Maintaining Isolator

The 1550nm Polarization Maintaining Isolator is a two port micro-optic device built with PM panda fiber. The PM isolator features low insertion loss, high isolation, high extinction ratio and high reliability and stability. The device guides optical light in one direction and eliminates back reflection and back scattering in the reverse direction. The device can be built with bare fiber, or 900um jacket cable.

Features

  • Low Insertion Loss
  • High Extinction Ratio
  • High isolation
  • Excellent stability and reliability

Applications

  • Fiber laser
  • Fiber amplifier
  • Fiber Sensor
  • Communications

The 1550nm Polarization Maintaining Isolator is a two port micro-optic device built with PM panda fiber. The PM isolator features low insertion loss, high isolation, high extinction ratio and high reliability and stability. The device guides optical light in one direction and eliminates back reflection and back scattering in the reverse direction. The device can be built with bare fiber, or 900um jacket cable. The PM Panda Fiber Isolator is widely used in amplifier systems, fiber optic systems and fiber lasers.

If you do not see a standard isolator that meets your needs, we welcome the opportunity to review your desired specification and quote a custom isolator. Requests for custom fiber pigtails, different wavelengths and handling power of operation or other specific needs will be readily addressed. DK Photonics can respond to custom requirements with short lead times.

Performance Specifications

Parameter

Unit

Specification

Operating wavelength

nm

1550

Grade

-

P

A

P

A

Type

-

Single Stage

Dual Stage

Operating Wavelength Range

nm

±20

Typ. Insertion Loss at 23℃

dB

0.4

0.5

0.5

0.6

Max. Insertion loss at 23℃

dB

0.55

0.65

0.65

0.8

Typ. Peak Isolation at 23℃

dB

42

40

58

55

Min. Isolation at 23℃

dB

28

26

48

45

Extinction ratio (Type B)

dB

≥20

≥18

≥20

≥18

Extinction ratio (Type F)

dB

≥22

≥20

≥22

≥20

Return loss (input/output)

dB

≥50/50

Fiber Type

-

PM1550-XP

Max. Power Handling (CW)

W

0.3, 1, 2, 5, 10

Max. Peak Power for Pulse

kW

/

Max. Tensile Load

N

5

Operating temperature

-5℃ ~ + 70℃

Storage temperature

-40℃ ~ + 85 ℃

Dimensions

mm

Ф5.5× L35(<5W), 65x12x9(>5W)

“B” for Both axis working, “F” for Fast axis blocking

  1. Above specifications are for device without connector.
  2. For devices with connectors, IL will be 0.3dB higher, RL will be 5dB lower and ER will be 2dB lower. The default connector key is aligned to slow axis. Power transmits through the connector less than 2W.
  3. If there is pulse application, please be sure to inform us of pulse energy and peak power.

 Package Dimension

1550nm Polarization Maintaining Isolator

Order information

P/N: PMISO-①-②-③-④-⑤-⑥-⑦-⑧

When you inquire, please provide the correct P/N number according to our ordering information and attach the appropriate description would be better. If need any connector, we do not recommend choosing a 250μm bare fiber pigtail.

Type

wavelength

Grade

Power Handling

Axis Alignment

Pigtail Diameter

Fiber Length

Connector

S: Single stage

D: Dual stage

15:1550nm

XX: Others

P:P Grade

A: A Grade

L: <0.3W

1:1W

2:2W

5:5W

10:10W

B: Both axis working

F: Fast axis blocking

25:250μm bare fiber

90:900μm Loose Fiber

XX: Others

08:0.8m

10:1.0m

XX: Others

00: None

FP: FC/PC

FA: FC/APC

XX: Others

Part Number Example: PMISO-S-15-P-L-B-90-10-FA

Description: 1550nm Polarization Maintaining single stage Isolator - 300mW, P grade, both axis working, 1.0m Fiber length with 0.9mm OD loose tube, and FC/APC connectors at all ports.

Ordering Information for Custom Parts:

If you need to customize other specifications, please provide detailed description for your requirement.

Optical Isolator Tutorial

Function

An optical isolator is a passive magneto-optic device that only allows light to travel in one direction. Isolators are used to protect a source from back reflections or signals that may occur after the isolator. Back reflections can damage a laser source or cause it to mode hop, amplitude modulate, or frequency shift. In high-power applications, back reflections can cause instabilities and power spikes.

An isolator's function is based on the Faraday Effect. In 1842, Michael Faraday discovered that the plane of polarized light rotates while transmitting through glass (or other materials) that is exposed to a magnetic field. The direction of rotation is dependent on the direction of the magnetic field and not on the direction of light propagation; thus, the rotation is non-reciprocal. The amount of rotation β equals V x B x d, where V, B, and d are as defined below.

schematic-diagram-of-faraday-effect

Figure 1. Schematic diagram of Faraday effect

Faraday Rotation

β = V x B x d

  • V: the Verdet Constant, a property of the optical material, in radians/T • m.
  • B: the magnetic flux density in teslas.
  • d: the path length through the optical material in meters.

Polarization-maintaining single-mode optical fiber isolator

1. Definition
The single mode optical isolator is a passive magneto-optical device which uses the Faraday effect of magneto-optic crystal to isolate the reflected light and only allows the light to transmit in a single direction. The optical fiber isolators are used to protect light sources from adverse effects caused by back-reflection or signal.
2. Characteristic

  • 1). Minimize Feedback into Optical Systems.
  • 2). Low insertion loss and high-power handling capability.
  • 3). Polarization independent structure.

3. Description
1). Introduction to the working principle of polarization dependent isolator
     Polarization-Dependent Isolators-Polarizer Type Polarization Dependent Isolator
The Forward Mode
In this example, we will assume that the input polarizer's axis is vertical (0° in Figure 2). Laser light, either polarized or unpolarized, enters the input polarizer and becomes vertically polarized. The Faraday rotator will rotate the plane of polarization (POP ) by 45° in the positive direction. Finally, the light exits through the output polarizer which has its axis at 45°. Therefore, the light leaves the isolator with a POP of 45°.In a dual-stage isolator, the light exiting the output polarizer is sent through a second Faraday rotator followed by an additional polarizer to achieve greater isolation than a single-stage isolator.
The Reverse Mode
Light traveling backwards through the isolator will first enter the output polarizer, which polarizes the light at 45° with respect to the input polarizer. It then passes through the Faraday rotator rod, and the POP is rotated another 45° in the positive direction. This results in a net rotation of 90° with respect to the input polarizer, and thus, the POP is now perpendicular to the transmission axis of the input polarizer. Hence, the light will either be reflected or absorbed. to achieve the function of light transmission in a single direction. This enables light to transmit in a single direction.

Structure schematic diagram of polarization dependent isolator

Figure 2. Structure schematic diagram of polarization dependent isolator

Usually, the PM fiber optical isolator with fast axis blocked, slow axis working is based on this structure. However, due to the limited withstand power of the polarizer, the average power of the isolator of this structure should not be greater than 2w, and higher power is recommended displacer type polarization dependent isolator. If you need to work with both axis, please refer to the principle of wedge type polarization independent isolator.

2). The main parameters
a. IL (Insertion Loss)
    Insertion loss refers to the additional loss caused by adding an optical isolator, and it is defined as the ratio of the optical power of the input and output ports of the optical passive components:
isolator
As shown in the formula above, Pout is the optical power of the output port, Pin is the optical power of the input port. The performance of isolator requires the insertion loss of forward light to be as small as possible. (Note: Generally, the calculation result is negative, but the negative sign is often omitted in practice.)
 
Schematic diagram of insertion loss test of the isolator
Figure 3. Schematic diagram of insertion loss test of the isolator
Take the red light as the example, the power for the input port Pin =100 mW, and the power of output port Pout=93 mW, so the IL of the channel 1 is:
IL = 10 × log (100/93)
= 10 × 0.032
= 0.32 dB
b. ISO (Isolation)
    Isolation refers to the isolation ability of the optical isolator to reverse reflected light. It is defined as the decibel ratio of the power value of the reverse incident optical signal to the power value of the reverse output optical signal:
isolator
As shown in the formula above, PRin is the power of the inverted input, PRout is the power of the inverted output. The performance of the device requires the bigger isolation, the greater the isolation value of reflected light, the better.
 
 Schematic diagram of isolation test of the isolator
Figure 3. Schematic diagram of isolation test of the isolator
Take the red light as the example, power of the inverted input PRin =100 mW, and thepower of the inverted output PRout=0.6 mW, so the IL of the channel 1 is:
ISO = 10 × log (100/0.6)
= 10 ×2.22
= 22.2 dB
 
c. Polarization Extinction Ratio (PER)
The polarization extinction ratio (PER) is a measure of how well a polarization-maintaining (PM) fiber or device can prevent cross coupling between the different polarization axes of the fiber. External stress on a fiber from sources such as heating, bending, or pulling can cause the PER to change.
Rotating Polarizer Method:
Rotating Polarizer Method is the most common method for measuring PER uses a low-coherence (unpolarized or circularly polarized) broadband light source and measures the extinction ratio with a linear polarizer and power meter.

The PER is measured using the following test measurement setup:

Schematic diagram of Measurement of Polarization Extinction Ratio setup

Figure 5. schematic diagram of measurement of polarization extinction ratio setup

Connect the components as shown above. Note that it is necessary to ensure that the panda eye of the PM fiber is perfectly aligned.

Adjust the rotatable polarizers sequentially until a minimum power value is measured by the power meter. Record the measured value as Pmin(dB).
Rotate the rotatable polarizers mount by 90°. Then record the measured value as Pmax(dB).
After Pmin and Pmax are measured, the extinction ratio can be calculated: PER(dB)= Pmax(dB) - Pmin(dB)

DK Photonics can provide a complete set of equipment/devices for the above measurement of extinction ratio setup, if you need it, please contact our sales: [email protected].