Add custom fields to simple product

Hi,

I’m using this approach to insert custom fields on a product.

add_action('woocommerce_product_options_general_product_data', 'woocommerce_product_custom_fields');

function woocommerce_product_custom_fields()
{
    global $product_object;

    echo '<div class=" product_custom_field ">';

    woocommerce_wp_text_input(array(
        'id'          => 'name',
        'label'       => __('name:', 'woocommerce'),
        'placeholder' => '',
        'desc_tip'    => 'true'
    ));

}

The problem is that this custom field appears in every product’s typology (simple, grouped, variable).

Is it possible to add this field only to the simple product ?